Checklist of UK Recorded Pteromalidae

Description & Statistics

Pteromalidae is one of the largest families of Chalcidoidea, with circa 570 valid genera and 2900 species. They are cosmopolitan in distribution. Important morphological characters include a usually 13-segmented antenna; parapsidal sutures distinct, but often incomplete; propodeum usually well developed. Pteromalids have been considered the most difficult Chalcidoidea to identify; morphologically they are exceedingly diverse, and thus no combination of taxonomic characters is reliable for identification.

Most Pteromalidae are primary parasitoids, but hyperparasitic species are common. Most species are ectoparasitic, but endoparasitic species are common also. Solitary and gregarious species and races are common. Generally, this family has a wide host range. Most species are gregarious ectoparasitoids of larvae and pupae of Lepidoptera and Coleoptera, but a number of species attack larvae and pupae of Diptera as well. Some are predaceous on eggs of Coccidae. There are no phytophagous species. Considerable importance has been placed on pteromalids for biological control of Lepidoptera, Coleoptera and synanthropic Diptera. A few species have also been used for the biological control of Coccidae.

Further Description.

Pteromalidae now also includes the former separate families, Cleonymidae, Miscogasteridae and Spalangiidae, which have been designated subfamilies Cleoneminae, Miscogasterinae and Spalangiinae, respectively. For the present, discussions of the various subfamilies will be separate because of considerable distinctness among them. The families consist of Asaphinae, Austroterobiinae, Austrosystasinae, Brachyscelidiphaginae, Ceinae, Cerocephalinae, Chromeurytominae, Cleonyminae, Coelocybinae, Colotrechinae, Cratominae, Diparinae, Ditropinotellinae, Eunotinae, Erotolepsiinae, Eunotinae, Eutrichosomatinae, Herbertinae, Keiraninae, Leptofoeninae, Louriciinae, Macromesinae, Miscogasterinae, Neodiparinae, Nefoeninae, Ormocerinae, Panstenoninae, Parasaphodinae, Pireninae, Pteromalinae, Spalangiinae and Storeyinae.

Among Chalcidoidea, the Pteromalidae are one of the most common families containing many genera and species of frequent encounter as parasitoids or hyperparasitoids of various insect pests. Dominant genera include Pteromalus, Habrocytus, Dibrachys and Pachyneuron. The family Spalangiidae is frequently included under Pteromalidae and is represented by many species of Spalangia (Bou…ek 1963). Most species are external gregarious parasitoids of larvae and pupae of Lepidoptera and Coleoptera, but some also attack pupae of Diptera and larvae of Hymenoptera. Genera such as Spintherus, Enargopelte and Peridesmia are egg predators. External and internal parasitism within a genus is found in Dibrachys, Pteromalus and Stenomalus. Ophelosia crawfordi Riley occurs as a predator on the eggs of Pulvinaria, Pseudococcus and Icerya (Smith & Compere 1931), and as a hyperparasitoid of these genera and sometimes of larvae of Coccinellidae. It has been reared from Icerya females where hyperparasitism seemed possible through Cryptochaetum. Some species of Asaphes are hyperparasitoids of Aphididae through various braconids, aphelinids and encyrtids that behave as primary parasitoids (Griswold 1929). Dibrachys cavus Wlk. (= boucheanus Ratz.) attacks a wide range of hosts with over 45 host species comprising 2 Coleoptera, 2 Diptera, 27 Hymenoptera and 14 Lepidoptera (Faure & Zolstorewsky 1925).

Pteromalus puparum L., a gregarious internal parasitoid of cabbage butterfly pupae and Ascia rapae L. in New Zealand have been credited with marked reductions in host population densities in biological control efforts. Species of Muscidifurax, Urolepis and Pachycrepoideus have been deployed successfully against synanthropic Diptera (Legner et al. 1976, Rueda & Axtell 1985).

Specific Geographic Areas

PALEARCTIC (EUROPEAN former USSR). - Dzhanokmen (1978/1987), as translated from the Russian, discussed this family as "This is the most common and richest chalcid family found in forest, forest-steppe, and steppe zones of the Palearctic. Trophic associations are highly variable, but the members of the family Pteromalidae are predominantly parasites of Diptera, Lepidoptera and beetles. The large subfamily Pteromalinae includes the largest number of genera of pteromalids, with the large subfamily Miscogasterinae next, and finally a few relatively specialized groups. Among these, distinguished by their biological specialization, are the subfamilies Cleonyminae (primarily parasites of larvae of wood beetles), Spalangiinae (parasites of Diptera), Eunotinae (larvae prey on eggs of coccids), and Asaphinae (secondary parasites of aphids, psyllids, and coccids). The keys given below include 196 genera with 703 species."

"The keys to pteromalids given here were mainly compiled on the basis of material provided by Graham 91969), including that housed in the Zoological Institute of the Academy of Sciences of the USSR, which was collected from the European part of the USSR as well as other areas of the Soviet Union."

"The terminology with reference to the body structure of pteromalids is unique in some respects."

"The abbreviation POL designates the distance between the inner margins of the posterior ocelli, and OOL designates the distance between the posterior ocellus and the margin of the eyes. Counting of the antennal segments begins from the basal segment (scape not included). The maximum number of segments in the antennal clava is three. For convenience, the so-called antennal formula has been used..."

"The broad apical part of the radial vein in the forewings of pteromalids has been termed the stigma, and the ascending apical section of the submarginal vein, the parastigma. Traces of veins which have disappeared are shown by dotted lines... and extant veins depicted as rows of hairs. Traditionally, these veins have retained the names of their correspondents (cubital and basal). The name of the areas enclosed by these "veins" on the wing disk has been retained, i.e., "cell" (for example, basal cell). The glabrous part of the wing disk, located immediately behind the basal vein is called the "speculum." The speculum may be either closed or open; in the former case it is restricted on the lower side by a row of hairs..."

NEARCTIC (CANADA). - Yoshimoto (1984) noted that "Pteromalide is the largest family of chalcidoids, and has the greatest diversity in size, shape, and biology. Most species are metallic in color and are recognized by the following characters: Head and thorax usually densely sculptured, with notauli complete, or incomplete; antennae 11-13-segmented (0-3 anelli, 4-7 funicle segments, 3 club segments). Propodeum usually with plicae (sublateral carinae), a median carina, and some species with a narrowed convex neck (nucha) extending posteriorly. Some of the smaller pteromalids are superficially similar to the Eulophidae but may be separated by the five-segmented tarsi, by the greater number of antennal segments (11-13), and by the long curved fore tibial spurs."

"Males of this family may be confused with those of the genus Eupelmus (Eupelmidae), in which the mesopleuron is divided by a distinct suture into mesepisternum and mesepimeron. Pteromalid males can easily be distinguished from eupelmus males, however, by the poorly developed mid tibial spur, which is enlarged and thickened in the latter. Females are indistinguishable."

Asaphinae. - There are 3 genera in this subfamily, but only Asaphes Walker is found in Canada. Species are distinguished by the following: head broader than thorax, lenticular; antenna inserted much below middle of face; antenna with 13 segments (1 or 2 anelli, 6 or 7 funicle segments, 3 club segments); marginal vein thickened; notauli complete; gaster petiolate; tergites 1 & 2 largest (Yoshimoto 1984).

This subfamily was revised by Graham (1969) who provided keys to European genera and species. All species are hyperparasitoids on various Aphidiinae (Braconidae) in aphids.

Brachyscelidiphaginae. - There is only one species Hemadas nubilipennis (Ashmead) of this subfamily in Canada. Riek (1970) placed the subfamily in the Pteromalidae.

The following distinguish this subfamily: generally smooth body; pronotum usually as wide as mesoscutum; notauli and inner margin of axillae close to each other; fore wing with radial cell fully or partially developed, without distinct stigma; basal cell bare or partially developed; hind wing with basal vein; hind coxa large, with apical margin exserted (Yoshimoto 1984). Gahan & Ferričre 91947) described and keyed the known genera and species. Species are generally gall formers.

Ceinae. - Canadian species of this subfamily are represented by a single species, Spalangiopelta ciliata Yoshimoto (Yoshimoto 1977a). The subfamily is distinguished by the following: bidentate mandibles; 13-segmented antennae (3 anelli, 3 club segments); antenna inserted above and lateral to clypeal margin; notauli distinct, complete; propodeum subhorizontal, slightly arched, with propodeal spiracles located halfway between anterior and posterior margins of sclerite; petiole distinct; gaster compressed laterally, and ovipositor prominent (Yoshimoto 1984).

The Ceinae have not been revised, and all species are parasitoids of dipterous leaf-mining Agromyzidae.

Cerocephalinae. - There are four genera of this subfamily in North America, Choetospila Westwood and Cerocephala Westwood being known from Canada (Yoshimoto 1984). The following characters separate this subfamily from other genera: globose or parallel-sided head; toruli separated by ridge; 5-6 segmented funicle, rarely with 7 segments in some males; fore wing often with tufts of hairs at proximal end of marginal vein, usually with two transverse fuscous bands; scutellum without frenal groove (Yoshimoto 1984).

The world Cerocephalinae was revised by Gahan (1946) and a key provided to the 8 known species. Hedqvist (1969) produced a key to 13 genera of Cerocephalini with synonymy, descriptions of new genera and species distribution and biological observations on world species. Grissell (1981) accepted two species of American Cerocephala, both of which were Holarctic. All species except one are parasitoids of coleopterous Curculionidae, Anobiidae, Bostrichidae or Scolytidae (Yoshimoto 1984).

Chalcedectinae. - There is one species, Chalcedectus texanus (Brues) in North America, from Texas. The subfamily is closely related to Cleonyminae. Yoshimoto (1984) reported that in the summer of 1981, Michael Sandborn of McMaster University, Hamilton, Ontario, collected 6 specimens of a possible new species, Chalcedectus Walker from Hamilton by malaise trap, which is ia first record for Canada.

The subfamily is recognized by the following: hind femora much swollen, with ventral serration or dentate; hind tibia arched as in Brachymeria (Chalcididae); fore femur swollen; tibial spur formula 1-1-2; prosternite flattened; postmarginal vein 2-3X longer than marginal, and stigmal vein short (6X as short as postmarginal vein); eyes strongly diverge ventrally (Yoshimoto 1984).

Chalcedectinae are generally known from the subtropics and tropics. The species are not well known, but parasitize wood-boring Coleoptera. Bou…ek (1959) synonymized 6 generic names under Chalcedectus, and listed 12 known species, mostly from the Neotropics.

Chrysolampinae. - In Canada the genus Chrysolampus Spinola represents this subfamily. Species resemble Perilampidae, but differ by having the following: prepectus separate from mesothorax; mandibles bidentate; head broader than thorax; pronotum margined posteriorly; stigmal vein subsessile; notauli complete; petiole longer than broad; tergites 1 & 2 cover entire gaster (Yoshimoto 1984).

These are parasitoids of Anobiidae (Coleoptera). In Europe other families of Coleoptera (Nitidulidae and Curculionidae) are parasitized (Yoshimoto 1984).

Cleonyminae. - There are 8 genera and 21 species of this subfamily in North America. Members are usually large and showy, and are better represented in subtropical and tropical areas. Two genera occur in Canada, Heydenia Förster and Ptinobius Ashmead. The subfamily is close to the Chalcedectinae and to the family Eupelmidae. Distinguishing characters are as follows: inner eye margin strongly diverging on lower part of head; antenna with 13 segments (either 1 annellus or 7 funicle segments, or without anellus and with 8 funicle segments); mandible bidentate or tridentate; pronotum large (ca. 1/2 length of or equal to mesoscutum). Notauli complete or incomplete; prepectus relatively large; fore femur enlarged, with one or more denticles; hind femur sometimes enlarged but without denticles; hind tibia with 2 spurs (Yoshimoto 1984).

The British and Swedish Cleonyminae were revised by Kerrich & Graham (1957). Bou…ek (1958) gave keys to genera and descriptions and notes. There are 40 genera and 170 species worldwide. Species are parasitoids of Cerambycidae, Buprestidae, Curculionidae and Scolytidae (Coleoptera), and of Vespidae and Megachilidae (Hymenoptera) (Yoshimoto 1984).

Colotrechinae.-- Only one species, Colotrechnus (Zanonia) ignotus Burks occurs in Canada (Burks 1958). It is distinguished by the following: antenna with 2 anelli in female, 3 anelli in male; scutellum with axillae produced forward much in advance of fore wing base; stigmal vein short, almost sessile; marginal vein 3-4X as long as stigmal vein; postmarginal vein short; hind tibia a bit compressed, with posterior edge bearing a row of spines with 2 strong apical spurs; hind coxa long (at least 3/4ths as long as femur); spiracle of propodeum touches metanotum; apical 2-3 tergites covered with dark bristles (Yoshimoto 1984).

Burks (1958) reared Colotrechnus ignotus from the heads of Compositae.

Cratominae. - In Canada the subfamily is represented by one genus, Cratomus Dalman. It is distinguished by the following: massive head; broad gena; clypeus with radiating striae extending to gena and face; inner orbit of eyes parallel; frons at times with hornlike projection; antenna with 8 segments (anellus absent, 3 funicle segments, 3 club segments); notauli incomplete, and sessile gaster. The biology is unknown (Yoshimoto 1984).

Diparinae. - There are six genera in North America, of which Trimicrops Kieffer, Dipara Walker, Netomocera Bou…ek and Lelaps Haliday are known in Canada. The Diparinae have the following characteristics: vertex with 6-12 obvious strong dark bristles; antenna with 1 anellus and 7 funicle segments in female (except Apterolelaps Ashmead, which has no anellus, and Trimicrops which has 3 anelli), and 1 anellus, 10 subequal flagellar segments, and an undifferentiated club in males; thorax with sparse, regularly spaced, bristly hairs; some adults are apterous but they usually have wings; hind coxa horizontally striate; gaster conically elongated with gastral tergite 2 ca. 1/2 to 3/4ths the total length of gaster in females, and tergite 2 almost covering entire gaster in males (Yoshimoto 1984).

The North American Diparinae were revised by Yoshimoto (1977b). Biologies are unknown, but members are possible parasitoids of either soil-associated insects or arthropods (Yoshimoto 1984).

Eunotinae. - There are 5 genera of Eunotinae in North America, of which Eunotus Walker and Scutellista Motschulsky are found in Canada. The following characters distinguish the subfamily: robust body; mesonotum, including axillae, in one longitudinal plane and slightly cylindrically convex; head wider than thorax; occiput broadly hollowed, crescentric; antenna with 6-10 segments (4 or 5 funicle segments), inserted near mouth margin; basal tergite of gaster largest, with hind margin straight; scutellum very much enlarged, and usually overlaps gaster (Yoshimoto 1984).

Eunotinae parasitize Coccoidea (Homoptera), and some species are hyperparasitic through Encyrtidae. Masi (1931) revised the Eunotinae of the world, providing a key to genera and species.

Eutrichosomatinae. - This subfamily resembles the families Eupelmidae, Perilampinae and the pteromalid Cleonyminae, Miscogastrinae and Pteromalinae. it occurs in America and Australia. Two species are known in Canada, Eutrichosoma mirabile Ashmead and Peckianus laevis (Provancher) (Bou…ek 1974). These are distinguished by the following: no coarse sculpture on body; body covered with hairs or scalelike hairs; head projects forward; antenna have 13 segments (1 anellus, 7 funicle segments, 3 club segments); weak antennal scrobe , with toruli close to each other and no interantennal ridge; mesoscutum with shallow complete notauli; axilla advanced forward of scutellar base and separated from both mesoscutum and scutellum by deep arched cross-groove; posterior margin of scutellum slightly overhangs metanotum in nearly vertical mode; prepectus small laterally, ventrally forming narrow connecting belt; postmarginal vein of fore wing short or undeveloped; tibia formula 1-1-2 (Yoshimoto 1984).

Bou…ek (1974) reclassified Eutrichosomatinae as a subfamily of Pteromalidae, and recognized 3 genera and 5 species. Eutrichosoma mirabile Ashmead is a parasitoid of Curculionidae (Coleoptera).

Macromesinae. - One species, Macromesus americanus Hedqvist occurs in Canada (Hedqvist 1960). The subfamily is distinguished by the following: 12-segmented antenna (1 anellus, 7 funicle segments, 2 club segments in female, and 7 funicle segments, 3 club segments in males); fore and hind tarsi with 5 segments; mid tarsus with 4 segments and with long basitarsus in female; inner orbits of eyes diverge greatly posteriorly; supplementary impressed line between malar groove and antennal toruli; notauli complete; posterior margin of propodeum almost truncate; postspiracular groove absent or weakly developed; basal vein of fore wing indicated by oblique pigmented spur for parastigma (Yoshimoto 1984). The subfamily has not been revised, and species are all parasitoids of coleopterous Scolytidae on coniferous.

Miscogastrinae. - This is the second largest subfamily in the Pteromalidae, which is divided into tribes, Micradelini, Pirenini, Ormocerini (= Tridymini), Trigonoderini, Sphegigasterini and Miscogastrini (Graham 1969). Graham (1969) also included a key to tribes of European Miscogastrinae. Tribal separation is unclear because of many character exceptions in each tribe. Generally, members of this subfamily are grouped together by the following: Notauli complete; hind tibia with 2 apical spurs; gaster petiolate (in most species of Miscogastrini and Sphegigasterini) (Yoshimoto 1984).

Micradelini are separated from Pirenini and Ormocerini by the postmarginal vein being much longer than marginal; speculum absent; 2-dentate mandibles; antenna in Pirenini with 10 segments and 11-12 segments in Ormocerini (Yoshimoto 1984).

There are 35 genera and 74 species in North America, placed in the 6 tribes. Of these, 17 genera are known in Canada. The tribes are represented by the following genera: Micradelini by Micradelus Walker; Pirenini by Pirene Haliday; Ormocerini by Gastrancistrus Westwood and Erixestus Crawford; Trigonoderini by Trigonoderus Westwood, Janssoniella Kerrich, Platygerrhus Thomson, and Gastracanthus Westwood; Sphegigasterini by Förster, and Cyrtogaster Walker; and Miscogastrini by Lamprotatus Westwood, Miscogaster Walker, Halticoptera Spinola, and Seladerma Walker (Yoshimoto 1984).

The North American genus Bubekia Dalla Torre with several species was revised by Gahan (1934). Graham (1969) revised Gastrancistrus Westwood of NW Europe. Species are all parasitoids of Aphididae (Homoptera), Agromyzidae, Tephritidae, Anthomyiidae or Cecidomyiidae (Diptera). Some species are parasitoids of Coleoptera, Hymenoptera or Lepidoptera (Yoshimoto 1984).

Panstenoninae. - In North America there is only one species, Panstenon columbianum Ashmead. This subfamily is distinguished by the following: head wider than thorax; antenna inserted high above middle of face; toruli near median ocellus; notauli complete or incomplete; marginal vein of fore wing 4-4.5X as long as stigmal vein; costal cell 12-20X as long as its max. breadth; legs reddish, except tarsi and trochanter; petiole and part of gaster at times reddish; basal tergite of gaster longest (Yoshimoto 1984). The subfamily has not been revised, and species are parasitic on Delphacidae (Homoptera).

Pteromalinae. - This heterogeneous subfamily is the largest with 68 genera and 195 species in North America. There are 47 genera and 110 species in Canada, represented by Dorcatomophaga Kryger, Pachyneuron Walker, Euneura Walker, Pachycrepoideus Ashmead, Rhaphitelus Walker, Cheiropachus Westwood, Dinotiscus Ghesquičre, Tomicobia Ashmead, Rhopalicus Förstr, Coelopisthia Förster, Dibrachoides Kurdjumov, Belonura Ashmead, Trichomalus Thomson, Diglochis Förster, Trineptis Girault, Dibrachys Förster, Trichomalopis Crawford, Lariophagus Crawford, Schizonotus Ratzeburg, Spaniopus Walker, Arthrolytus Thomson, Psychophagus Mayer, Metastenus Walker, Homoporus Thomson, Merisus Walker, Callitula Spinola, Cecidostibia Thomson, Catolaccus Thomson, Zatropis Crawford, Pseudocatolaccus Masi, Muscidifurax Girault & Saunders, Nasonia Ashmead, Dinarmus Thomson, Pteromalus Swederus, Habrocytus Thomson, Lonchetron Graham, Anisopteromalus Ruschka, Hypopteromalus Ashmead, Hemitrichus Thomson, Norbanus Walker, Lampoterma Graham, Neocatolaccus Ashmead, Capellia Delucchi, Arachnopteromalus Gordh and Habritys Thomson. With the present classification, Peromalinae is placed as a single subfamily without tribes. The difficulty lies in this group's separation from some Miscogastrinae because it requires combinations of several characters for separation. Generally members of Pteromalinae have the following characteristics: notauli incomplete; hind tibia with one apical spur; petiole sessile or subsessile; fore wing with marginal vein either not thickened or partially to entirely thickened throughout (Yoshimoto 1984).

The following genera have been revised n North America: Arthrolytus Thomson (Burks 1969), Metacolus Förster (Burks 1965), Dinotiscus Ghesquičre (Crawford 1912), Cheiropachus Westwood (Gahan 1938), Catolaccus Thomson (Crawford 1907), Muscidifurax Girault & Saunders (Kogan & Legner 1970), Lariophagus Crawford (Gahan 1927), Zatropis Crawford (Crawford 1921), Tritneptis Girault (Burks 1971), Habrocytus Thomson (Girault 1917), and Dorcatomophaga Kryger (Yoshimoto 1976).

The Pteromalinae show diverse behavior, and contain species reared from nay kinds of insects and other arthropods. Some examples are Rhopalicus parasitizing Scolytidae; Anisopteromalus and Dinarmus parasitizing Bruchidae; Pseudocatolaccus parasitizing Cecidomyiidae; Muscidifurax and Nasonia parasitizing Muscidae and Calliphoridae; Gomicobia parasitizing Scolytidae; Trichomalopis and Dibrachys parasitizing Thomisidae (Araneae) and Aphidiidae (Hymenoptera); Arachnopteromalus dasys Gordh attacking the egg sac of Uloboridae (Araneae). Diverse behavior is also shown within a closely related group of species and subspecies, the Muscidifurax. Although taxonomic differentiation of this genus into its 5 identified species is difficult, relying heavily on male genitalia, behaviorly there are great differences shown in courtship, gregarious or solitary oviposition, size, unisexual and bisexual reproduction, etc. (see sections on Medical/Veterinary entomology and Reproduction).

Spalangiinae. - This subfamily is distinguished by the shiny black color; head and dorsum of thorax punctated; notauli complete; antennal toruli touch the lower edge of face and are located a bit above the ventral level of clypeus; antenna do not have ring-like segments, and the funicle bears 7 segments; hind tibia has a single spur; and the gaster is petiolate.

The genus Spalangia Latreille was revised by Bou…ek (1963) who provided keys to Holarctic, Ethiopian, Oriental and Neotropical species and a host-parasitoid list. All Spalangia spp are parasitoids of dipterous puparia (Muscidae, Calliphoridae, Sarcophagidae, Drosophilidae and Chloropidae) associated with animal wastes, carrion and decaying plants (Yoshimoto 1984).

AFRICA.-- Prinsloo (1980) commented that "The pteromalids form an extensive family, and it has been stated that it is perhaps one of the most difficult groups of the Hymenoptera to deal with taxonomically. it is thus not surprising that there is little agreement on the limits of this family. Groups such as the Eucharitidae, Ormyridae and Perilampidae, all treated here as families, have been placed as subfamilies of the Pteromalidae, whereas subfamilies of the latter, such as the Cleonyminae, Spalangiinae and Miscogasterinae, have been given family rank by some authors."

"Because of the great diversity in structure, taxonomic difficulties on the limits of the family, and the poor state of our knowledge of these insects in Africa, it is possible only to give a generalized diagnosis of the family here. The keys should suffice for recognition of the family, with few exceptions. it is also beyond the scope of this study to deal with all the numerous subfamilies, of which more than 15 are recognized."

Diagnosis. - "Moderate to large chalcidoids; colour often blackish or metallic green, but also paler; antenna usually with more than one ring-segment; mesoscutum with complete or incomplete parapsidal sulci; fore wing with venation well developed, the marginal vein usually relatively long; shape of abdomen varying considerably: gaster broadly joined to propodeum or petiolate, the petiole sometimes long and slender; gaster ranging from short and broad to long, slender, acutely pointed at apex; tarsi five-segmented, the fore legs rarely with femur enlarged, swollen, or with hind femur swollen as in Chalcididae."

Biology. - "The great majority of pteromalids are primary or secondary parasitoids, attacking a large range of insects in their various stages of development, whereas a few are known to be gall-formers. One such species is Asparagobius braunsi Mayr which is endemic to South Africa, and which is a gall-former on the stems of Asparagus stricta. A number of pteromalids are important enemies of Diptera, and several species of Spalangia have been recorded as solitary external parasitoids of the puparia of fruit flies, whereas S. endius Walker is a common cosmopolitan parasitoid of housefly puparia; Nasonia vitripennis (Walker) is another widespread species which is a primary pupal parasitoid of various Diptera, mainly of the families Calliphoridae and Muscidae, and Muscidifurax raptor Girault & Saunders [= Sanders] readily attacks housefly puparia in many parts of the world. Species of Pachyneuron are primary parasitoids of syrphid flies, but have also been recorded as hyperparasitoids of braconid wasps attacking aphids. Many pteromalids are parasitic in Coleoptera, some of which belong to economic important groups. Members of the Chalcidectinae attack xylophagous beetles; Choetospila elegans Westwood, which is cosmopolitan in distribution, develops from a number of stored grain beetles of the families Curculionidae, Anobiidae, Bruchidae and Bostrichidae, and also from moths of the family Gelechiidae, whereas species of Dinarmus are well known parasitoids of bruchid beetles. Many species of Lepidoptera also serve as hosts. Species of Pteromalus and Habrocytus are often reared from butterflies, and the cosmopolitan P. puparum (L.) is known to attack the lucerne butterfly, Colias electo (L.) in South Africa. Scutellista is one of the few genera that parasitize Coccoidea, and its species are important natural enemies of injurious soft scale insects and mealybugs. Species of this genus are also predaceous on the eggs and larvae of their hosts."

African Pteromalidae as mentioned above, only the more common subfamilies and genera are referred to here. Of the several hundreds of species recorded from Africa, the majority are poorly known and usually unrecognizable from their descriptions.

"Species of Spalangia (Spalangiinae) are usually black, without metallic refringence, the body somewhat flattened dorsally, the head directed forwards, and the head and thorax with conspicuous piliferous punctations. The Cerocephalinae is related to the Spalangiinae, and here represented by Choetospila elegans Westwood, a cosmopolitan species which is also somewhat flattened dorsoventrally and in which the head and body are smooth, shiny, without differentiated sculpture. Scutellista (Eunotinae) is a peculiar beetle-like wasp which is black, very stout-bodied, with a large shield-like scutellum produced aver the abdomen, giving the insect a hump-backed appearance. Oodera (Cleonyminae) is a rather unusual pteromalid that has been placed in the Eupelmidae; it has the fore femur enlarged, serrated along the ventral margin. The Pteromalinae is by far the largest subfamily, including many important genera such as Nasonia, in which the wings are reduced in the male; Pachyneuron with the marginal vein of the fore wing thickened; and Pteromalus. Members of the subfamily Diparinae do not resemble typical pteromalids; they are often slender, brownish or yellowish in colour, with a well developed gastral petiole; in the female the wings are often reduced in size. The Chalcidectinae is a poorly known group of unusual pteromalids which have the hind femur enlarged, swollen and ventrally toothed, as in the Chalcididae. The Brachyscelidiphaginae are interesting in that the species are phytophagous, represented in this region by Asparagobius, a large robust pteromalid which is black with a strong metallic lustre."

INDIA & ENVIRONS.-- "Farooqi & Subba-Rao (1988) noted that "The family Pteromalidae constitutes one of the largest families of Chalcidoidea. It contains as many as 600 genera and approximately 3,000 species. As regards India and the adjoining countries, the number is too less. Bou…ek et al. (1978) recorded a total of 112 species grouped under 80 genera."

"The host range of Pteromalidae is sufficiently wide and include both entomophagous and phytophagous forms. The entomophagous species attack important insect Orders like Lepidoptera, Coleoptera, Diptera, Rhynchota and Hymenoptera. Most of them being primary parasites but secondary ones are also not uncommon. The phytophagous forms develop on stems of grasses, in seeds or produce galls. These mostly occur in the subfamilies Brachyscelidiphaginae and Epichrysomalinae."

History. - "A review of literature reveals that from the Indian subcontinent the only work produced was a catalogue by Mani in 1938 where 23 genera and 41 species were catalogued under two families i.e. Pteromalidae and Miscogasteridae. Later on Pruthi & Mani (1940) published biological notes on several of the present day pteromalid species. Among those who contributed to the faunistics and taxonomy of the Indian Pteromalidae in the form of isolated papers, mostly containing descriptions of some species, mention may be made of Ahmad & Mani (1939), Bhatnagar (1952), Cameron (1891, 1906), Crawford (1913), Dutt & Ferričre 91916), Ferričre (1930, 1931, 1939), Gahan (1919, 1925), Howard (1896), Mani (1939, 1942), Mani et al. (1973, 1974), Masi (1924, 1927), Narayanan et al. (1957), Farooqi & Menon (1973, 1974), Bou…ek (1973, 1978) and Bou…ek et al. (1978). It was Bou…ek et al. who tried to project a more complete picture of the Pteromalidae of India and adjoining countries. In the present key all genera mentioned by these authors have been included, even when several of them are still reported to occur with unidentified species."

"The review published by Bou…ek et al. (1978) shows that the fauna of this region is not isolated from the rest of the world. Many Palaearctic and circum-tropical species are represented here. This may be evident from the fact that genera like Miscogaster, Notoglyptus, Merismus, Callitula, Syntomopus, Chlorocytus etc. which are known only from Europe are now found to be of frequent occurrence in India. However, a few show somewhat restricted distribution, like Agiommatus, Ecrizotomorpha, Manineura and Asoka."

Classification. - "The taxonomic boundaries are still not too clearly defined. In the present work we have followed the classification given by Graham (1969) (see also Bou…ek et al. 1978)." A key to the genera of Pteromalidae of India is given in Farooqi & Subba-Rao (1988).

AUSTRALASIA.-- Bou…ek (1988) noted that "'Pteromalini,' the second earliest available group name in the Chalcidoidea, was proposed by Dalman (1820)."

"This family is very rich and very diverse in forms. Within the Chalcidoidea, the Pteromalidae are rivalled only by the Encyrtidae and in terms of the number of recognised genera and species. There is some regional variation, with probably relatively fewer species of pteromalids in the tropics than in temperate regions. The family, however, includes a much wider variety of forms than the two other names families together. This great diversity has repeatedly led to the separation of some groups as independent families, especially 'Miscogasteridae,' 'Spalangiidae,' 'Cleonymidae' and 'Tridymidae' (e.g. Nikolskaya, 1952). Conversely Riek (1970) expressed a broader view by including the Ormyridae, Perilampidae and Eucharitidae in Pteromalidae."

"The limits of the family are not yet satisfactorily stabilised, in spite of recent considerable advances in knowledge. The status of Ormyridae, Perilampidae and Eucharitidae is discussed in more detail under their respective headings. The placement of the Epichrysomallinae and perhaps some other groups, which are here included in Agaonidae, is also somewhat contentious."

"The back of the head provides some useful taxonomic characters which have been overlooked in the past, e.g. in the postgenal bridge and exposure or concealment of the maxillaria (the term used e.g. by Ross, 1937: 129), but their interpretation seems difficult. In some cases the bridge may be closed secondarily, perhaps in association with the development of the prognathous position of the head. In the Pteromalinae, with the head orthognathous, the back of the head always has a broad channel between the oral fossa and foramen magnum... Other characters, such as the elongate cerci present in a few genera, are apparently plesiomorphic."

"Miscogasterinae, Ormocerinae and Cleonyminae are separated from Pteromalidae as families by Walker (1833: 370), but he based this only on some vague characters observed in a few British species. Westwood (1839) added 'Spalangiides' and also placed Torymidae in 'Pteromalides.' Haliday (1843) separated 'Pireniani.' Förster (1856) attempted a further elaboration of the system, treating all the previously proposed groups as different families. This was changed by Thomson (1876, 1878), who replaced Ormocerides by Tridymina, and accepted as 'tribes' (now regarded as subfamilies) Pirenina, Spalangiina and Pteromalina, the last one with several subtribes, including 'Mischogastrides' and 'Cleonymides.' Thomson's system became the basis for Ashmead's concept, best known from his 1904 Classification. He divided the species now included in Pteromalidae into 3 families: Miscogasteridae (with 4 subfamilies), Cleonymidae (2 subfamilies) and Pteromalidae (6 subfamilies). Ashmead's system was largely followed by Girault. Later on the 3 families were united again in Pteromalidae by Peck (1951; based on A. B. Gahan's views), with subfamilies Spegigasterinae and Pteromalinae, each with 9 tribes. The publication of Nikolskaya (1952), written before the war (pers. comm.), has the pteromalids still in 5 families. Later developments are summarised in Graham's (1969) classical treatment of the European Pteromalidae, which has had a major impact on the classification of the family."

"Even in Europe the family is poorly known in comparison with other insect groups, despite the work done since about 1950, by Graham, Bou…ek, Delucchi, Rosen, Hedqvist and a few others. Apart from Graham's monograph (1969) keys to the European genera by Bou…ek (in Peck & al., 1964) are still useful. More recently extensive studies have been undertaken in North American (especially Grissell), Japan (Kamijo), Africa and India (Bou…ek and others). However, no extensive generic keys to these faunas have been published so far, except for a key to the Indian genera by Farooqi & Subba Rao (1985)."

"Of the 15 subfamilies recognised in Europe by Graham (1969) only 12 are also represented in the Australo-Papuan region; one of them is here transferred back to the Perilampidae. Altogether 28 subfamilies are defined here, although almost half of them are based on single or very few genera. Some of these subfamilies are upgraded groups from Graham's classification, others are exclusively or mainly of southern distribution. The groups are here recognised mainly because they seem to constitute natural (?monophyletic) units; but their status may be changed in the future. In some cases the previous system was difficult to maintain. For instance, Miscogasterinae seem to lack tangible characters as a group and some taxa, included there by Graham, are transferred to Pteromalinae (including the Sphegigasterini). Some taxa given tribal status by Graham are treated as subfamilies, e.g. Ormocerinae and Pireninae. The present subfamily Miscogasterinae largely corresponds to Graham's Miscogasterini, but is represented here only by 4 genera, apparently being much richer in forms in the northern temperate zone. Miscogasterinae probably include only parasites of Diptera and are replaced in Australia by a variety of 'petiolate' Pteromalinae, especially forms earlier classified as Sphegigasterini. Some characters, including the complete or obliterated notaular grooves and a short or long gastral-petiole, seem to have been given undue weight in the past. In the Australian region the latter character states (regarded as apomorphic) apparently developed independently in many evolutionary lineages. Sometimes differences between the Pteromalinae, Pireninae, Miscogasterinae and Chrysolampinae are observed in various other characters, especially in the form of the pronotum, of the propodeum with the petiole, and of the lower face but it is difficult to express, define and use these differences. Perhaps more detailed studies of morphology (as e.g. current studies of the labrum and of the thorax musculature by C. Darling and G. Gibson, respectively) will lead to confirmation or refutation of various ideas on the relationships of the groups involved and of their phylogeny."

Biology. - "The great diversity of body forms partly reflects the wide variety of biological aspects. Pteromalids include parasites in eggs, larvae and pupae from many orders of insects; a few species even oviposit into adults of some beetles (Curculionidae, Scolytidae). The larvae of some other pteromalid species develop as predators on eggs, e.g. of coccids (Eunotinae) or of spiders. Many pteromalids are known to be primary parasites, secondary and sometimes even tertiary or quaternary parasitism is known. Pteromalids inhabit almost all terrestrial ecosystems. A number of groups, including Ditropinotellinae, Ormocerinae, Austrosystasinae and possible Coelocybinae and partly Colotrechninae are known to be, or surmised to be, phytophagous. Some of them develop in seeds of plants, many are reared from galls and some Ormocerinae are known to be gall-makers, e.g. an Australian Trichilogaster species which controls an Acacia growing as a weed in South Africa. Some other species may be inquilines in galls caused by other insects, consuming the tissues at the expense of the actual gall-maker. Of the entomophagous forms on the other hand Cleonyminae, Leptofoeninae, Macromesinae and Cerocephalinae are probably exclusively parasites of beetles, mainly of species developing in woody plants. Diparinae as far as is known attack curculionids (and perhaps other beetles) on roots or parts of plants close to the ground. Asaphinae, Elatoidinae and Eunotinae are mainly associated with homopterous insects, especially coccids, aphids and psyllids. Spalangiinae, Herbertiinae, Miscogasterinae and many 'petiolate' Pteromalidae develop at the expense of dipterous larvae and puparia. The subfamily Pteromalinae attack hosts belonging to several orders, the more plesiomorphic forms attack mainly beetles. In general the plesiomorphic forms of the family belong to two different ecological groups: the beetle parasites and the phytophagous species. it is, however, very difficult to judge from the morphology which of the two is more ancestral. Probably it is the phytophagous groups, but in that case phytophagy would seem to have a plesiomorphic character, not really useful in phylogenetic speculations."

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Biology & Behavior

Extensive studies have been made on species in the genera Dibrachys, Dibrachoides, Pteromalus, Eupteromalus, Habrocytus, Muscidifurax and Nasonia (Mormoniella).

Variation within a genus and species is aptly demonstrated in the genus Muscidifurax, which is a group of closely related species (superspecies) attacking puparia of synanthropic Diptera. The five described species occur in geographic isolation in the Nearctic and Neotropical regions, except two species which are sympatric in the western Nearctic (Legner 1969, 1983, Kogan & Legner 1970, Kawooya 1983). The suspected ancestor of this apparent clade, M. raptor Girault & Sanders, is widely distributed in Europe, Africa, North America, and portions of the Pacific area (Legner & Olton 1988, 1971; Legner et al. 1976, Rutz & Axtell 1980, Legner 1987, Smith et al. 1987), but it has not been found in the Neotropics. There are no known clinal patterns. The genus has not been reported from Asia and is poorly represented in equatorial regions (Legner & Olton 1968, Legner & Greathead 1969, Legner et al. 1976, Legner 1983).

Muscidifurax are most prevalent in or near accumulated decaying organic material deposited by humans and livestock, where they parasitize host Diptera that also breed selectively in this habitat. Therefore, they fit the endophilous synanthropic category (Povolny 1971, Legner et al. 1974), and their existence depends largely on herdsmen. This has led to the suggestion that the four species currently confined wholly to the Americas could have evolved within the recent time period of European settlement, or during the past 400 yr (Kogan & Legner 1970, van den Assem & Povel 1973).

The only known South American member of the genus, M. raptorellus Kogan & Legner, occurs as three or more separate populations. One population from coastal Peru is solitary, whereas the others show various degrees of gregarious oviposition and development (two or more eggs laid at one insertion) (Legner 1967, 1988, Kogan & Legner 1970, Kawooya 1983). One of the gregarious populations from central Chile oviposits more than one egg in >60% of the hosts it attacks, with subsequent successful gregarious development. The Chilean population compensates for a lower host-searching capacity with the gregarious behavior, which results in a greater number of progeny per host (Legner 1967, 1987).

Adult Habits.

The time between emergence of adults and oviposition is short. Females of Nasonia vitripennis Wlk. (= Nasonia brevicornis Ashm., Mormoniella vitripennis Wlk.) deposit eggs within three hours of emergence, and Habrocytus cerealellae Ashm. does so the following day. Two to three days are required by Dibrachoides dynastes Foerst. and Homoporus braconidis Ferr. for gestation, but Pirene graminea Hal. lays its first eggs 7-8 days after adult emergence (Clausen 1940/1962).

As is typical for Hymenoptera, adults feed extensively on honeydew, and plant secretions. Such food is sufficient to maintain life, but in many species it is not sufficient to meet the optimal nutritional requirements for egg production. It was demonstrated that a protein diet is essential for some species before normal oögenesis can proceed. The body fluids of the host provide a suitable food of this type, and the females of Pteromalidae more generally than of any other family, have developed the habit of feeding on fluids that exude from punctures made with the ovipositor. Roubaud (1917) seems to be the first to realize the significance of host-feeding, as his work with Nasonia vitripennis showed that such feeding was essential before normal oviposition could take place. Such feeding may be associated with and immediately precede oviposition, or the two acts may be entirely independent and upon different host individuals (Clausen 1940/1962, Legner & Gerling 1967). Feeding on exposed hosts presents minimal difficulties for the parasitoid, but where hosts are sequestered in a burrow, cocoon, cell or puparium, direct feeding is not possible. Therefore, it is necessary to provide some means by which the body fluids of the host can be brought within reach of the parasitoid. This is accomplished by the construction of a feeding tube which extends from the oviposition puncture in the host's body to the outside wall of the cell, etc. Fluids rise to the top of the tube by capillary action and are there lapped up by the parasitoid. In some species, withdrawal of the body fluids is so great as to suggest the deployment of actual suction to bring it to the surface.

This adaptation for feeding was first discovered by Lichtenstein (1921) while studying Habrocytus cionicida Licht. and external parasitoid of larvae and pupae of the weevil, Cionus thapsi F., in their cocoons. The habit has since been found in many other genera of Pteromalidae and occasionally in other Chalcidoidea as well. It also occurs among the Braconidae, particularly in the genus Microbracon. A detailed account of the manner of tube formation was given for Habrocytus cerealellae, parasitic on the angoumois grain moth Sitotroga cerealella Oliv. (Fulton 1933). This parasitoid normally attacks larval stages in cells in the seed, although parasitization and development are also possible on exposed larvae. A feeding tube is constructed only when the host is deeply embedded in the seed, however. After stinging, the ovipositor is withdrawn until only its tip penetrates through the hole in the cell wall. A clear, viscid fluid begins to ooze from it, most abundantly from near the tip. This material is spread by a twisting and vertical movement of the ovipositor, which serves as a spatula. It is worked downward gradually, and fresh material is added continuously until the body of the host is finally reached. The ovipositor tip is then slowly moved about until the original puncture in the skin is found. It is then reinserted in the puncture and held in that position for several minutes, during which time the tube is completed. The ovipositor is withdrawn very slowly in order not to damage the delicate tube. In the meantime, the stylets move alternately up and down. A small extension of the tube appears above the surface of the opening in the cell wall. The female then turns about and begins feeding on the fluids from the tube, which may continue without interruption for almost an hour. At the completion of feeding, the female reinserts the ovipositor in the tube, seemingly for the purpose of breaking it. Some researchers have noted this reinsertion of the ovipositor by different species and considered it to be for the purpose of inducing a renewal of body fluids flow and that breaking the tube was only accidental.

Faure & Zolstorewsky described an identical manner of tube formation in Dibrachys cavus. H. D. Smith (1930) observed in Dibrachoides dynastes Foerst., that the chalky fluid flows down the full length of the ovipositor while its tip is still inserted in the wound, with hardening taking place quickly after which the ovipositor was cautiously withdrawn. Flanders (1935b) noted tube formation among egg predators. Female Spintherus sp. punctured one of a cluster of eggs of the alfalfa weevil, Hypera variabilis Hbst., that were embedded in a plant stem. A tube was formed and the entire egg contents was sucked out. Colleterial glands are thought to be the source of the tube substance.

Detailed studies of the relation of the feeding habit of Peridesmia and Spintherus to egg development were made by Flanders. Sufficient protein was not stored up during the larval period to provide for egg production, which must be accounted for later. The preference for host fluids is shown only during oögenesis and maturation. This reaction first appears about six days before egg deposition. If environmental conditions were adverse, the ovarian follicles were absorbed, feeding hon host fluids ceased, and a long period of reproductive inactivity followed. The degeneration of the ovaries under such conditions was considered to be a form of phasic castration. The induced inactivity corresponded in time to periods of low numerical status of the host stage that was subject to attack. It may have a direct effect on the ability of a parasitoid species to survive where the host undergoes long periods of aestivation.

The female is able to develop and deposit eggs for a certain period as a result of feeding on protein substances, but carbohydrates are necessary to provide the energy required for extended activity. Females of Pteromalus puparum deposited eggs for a period of three weeks when confined with fresh host pupae, to which they were limited for food, while with the addition of honey they continued oviposition for two months (Doten 1911).

Most species that attack larvae of Lepidoptera and Coleoptera permanently paralyze the host prior to oviposition. This is especially true in Habrocytus, Dibrachys and Dibrachoides and some other less common genera. In H. cerealellae the parasitoid pumps several droplets of a paralyzing fluid into the host body, which can be readily seen as it flows down the ovipositor. This organ is thrust deeply into the host to ensure thorough distribution of the fluid. The stinging act requires up to 10 min., and the host is completely paralyzed before the ovipositor is withdrawn. In Drabrachoides dynastes the host may be stung 3-100 times before complete immobility, which may take up to 8hrs (Clausen 1940/1962). The larvae of the bee moth, Galleria mellonella L., die from the effects of the sting of Dibrachys clisiocampae, and the eggs of the latter are not deposited until death occurs. Doten reported that larvae of the codling moth and pupae of the cabbage butterfly were usually killed by thrusts of the Meraporus sp. ovipositor. In a large number of species hosts are consistently killed by the sting, and decay ensues very soon thereafter. In such cases the larvae are scavengerous in habit rather than parasitic. A few species do not paralyze the host, among which are Trichomalus fasciatus Thoms., an external parasitoid of Ceutorrhynchus assimilis Payk. larvae. Pirene graminea paralyzes its host larva Contarinia pisi Winn. temporarily (Clausen 1940/1962).

Some species that are parasitic in dipterous, seal the puncture in the puparial wall with a drop of fluid after oviposition. Clausen (1940) noted the behavior of Scymnophagus townsendi Ashm., an external parasitoid of Scymnus sp. pupae, a coccinellid predator on aphids in Japan. During oviposition the female stands on the exposed portion of the dorsum of the pupa and makes a preliminary insertion with the ovipositor to form a feeding puncture. Several hours may be spent in lapping up the body fluids exuding from the wound, after which the ovipositor is reinserted, usually in the original puncture, and forced completely through the body. The egg is laid on the ventral surface of the abdomen or under a wing pad or leg. Feeding and oviposition may be repeated, the single original puncture serving for this purpose. A compact cluster of 4-6 eggs is usually found when the host is finally abandoned.

Fulton (1933) described the mechanics of oviposition in H. cerealellae, noting the presence of a remarkable adaptation for the passage of a large object through a relatively minute tube such as the ovipositor. The small end of the egg approaches the ovipositor first; the spicules of the chorion, in conjunction with the backward directed spines and ridges on the walls of the vagina and stylets, prevent any backward movement once the surfaces are engaged. The greatly compressed egg tip is drawn down through the ovipositor. The chorion, being stretched, passes down the ovipositor by a pulling action rather than any pressure exerted through the abdomen. Therefore, the portion of the chorion being drawn through the tube is almost devoid of liquid content, and little lateral pressure is exerted on the ovipositor. At this time the stylets, moving together rather than alternately, work the tip of the egg downward until it reaches the end of the ovipositor. Thereafter the egg contents flow down the tube into the released portion, and by this action the remainder of the egg is pulled through the ovipositor. The reduction of egg diameter during its passage down the ovipositor is shown by a comparison of egg size with ovipositor width. The egg averages 0.16 mm in width, while the outside diameter of the ovipositor is circa 1/5th of this, or 0.03 mm.

The habit of adult swarming, which is rate in Chalcidoidea, was recorded for Pteromalus deplanatus Nees (Scott 1919). During 1916-1919 in some localities in England this species was present in huge swarms in buildings during late July and August. Clausen (1940) believed this to be a search for suitable quarters in which to pass the winter.

Reproductive capacity of Pteromalidae is high. An egg deposition of 676 in 78 days has been recorded by Fulton for H. cerealellae, and P. puparum has been found to lay as many as 697 eggs. A single female Nasonia vitripennis produced 557 progeny (Cousin 1933), suggesting an egg capacity much in excess of that number. A series of Eupteromalus nidulans Thoms. females laid an average of 251 eggs, with a maximum of 583 (Proper 1931). Aplastomorpha calandrae How. lays ca. 250 and Dibrachoides dynastes a maximum of 122 during a single month.

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Immature Stages of Pteromalidae

The eggs of the great majority of the species of the Pteromalidae are ovate, ellipsoidal, or cylindrical in form, often slightly curved, and without an anterior stalk or pedicel of any sort. That of Enargopelle ovivora, however, is an exception in that it has a slender stalk, one third as long as the egg body, at the broader end. In many species, the chorion is smooth and shining; in others, it is covered with minute spines or spicules, but with the poles bare (Fig. 46). These spicules often give the egg a greyish color. The eggs of Dibrachys cavus, Stenomalus muscarum and Habrocytus trypetae Thoms. are covered with "tubercles," or papillae; those of Pachyneuron coccorum L. have a granulate surface. In Dibrachoides dynastes, the chorion bears longitudinal ridges. The sculpturing of the egg is not uniform even within a genus, as shown by the smooth glistening egg of Pteromalus puparum and the spinose chorion of that of P. variabilis Ratz. The sculptured chorion is found only upon eggs that are deposited externally.

Development of Larvae.

The larvae of practically all species are hymenopteriform with 13 distinct body segments, the head often large, and the integument bare except for three pairs of setae on each of the thoracic segments and two pairs on those of the abdomen, the four pairs of spiracles are situated on the second thoracic and the first three abdominal segments (Fig. 47A). There appears to be a variation among the species in the num­ber of sensory setae. The body of Stenomalus micans is covered with minute integu­mentary setae, and the last abdominal segment is modified to form a "furca" which serves to hold the larva in a favored feeding position. Habrocytus sp. reared from braconid cocoons by Voukassovitch (1927) has a sucker like organ ventrally on the second thoracic segment, which is stated to serve a locomotory function. Merisoporus chalcidiphagus W. & R. has an additional pair of spiracles, which is on the third thoracic segment. Certain of the endophagous species, such as Pteromalus puparum, lack an open tracheal system.

The larva of Pirene graminea, described and figured by Kutter (1934), departs from the normal of the family and Is distinctly mandibulate in form. The head is large, the body segmentation indistinct, the integument without setae, and the large, extruded, falcate mandibles are very widely spaced and lie transversely. Marchal (1907) described a larva of similar form in Tridymus piricolaa Marchal.

First instar larvae of species that feed externally are usually very active, moving about readily on the body of the host and in the cell containing it. However, Smith (1930) found that larvae of D. dynastes which hatch from eggs not placed directly on the host, usually die without reaching it. In solitary species, there is a pronounced cannibalistic tendency, and the larva that hatches first often destroys any remaining eggs. In cases where a number are able to hatch, the youngest, due to its greater mobility, is usually victorious in the combat for the host. Such an elimination of surplus individuals seems necessary because of the indiscriminate oviposition of the parent female, which is apparently unable to recognize hosts that are already parasitized.

Many individuals of Pteromalus puparum develop within a single host pupa, which results in the colony being too large for the available food supply. Numerous dead larvae are often found at the extremities of the pupa, these having died from starvation (Hardy 1933). It is evident that the food material at these points is exhausted more quickly than at the middle of the body, as Faure (1926) found that development of individuals in the extremities of the host is retarded. But Voukassovitch (1926) concluded that the retardation in emergence of a portion of the brood is independent of nutrition. It was found that emergence from pupae that had been parasitized on known dates often extended over several months. This appears to be a larval diapause of uncertain duration and affects a varying portion of each colony. Clausen (1940) regarded it unusual for the individuals comprising a single colony of an internal parasitoid to emerge so irregularly, and noted that it contrasts sharply with the synchronous development and emergence of polyembryonic Encyrtidae, which encounter the same adverse conditions through overcrowding, etc. However, Legner (1969) found that a spread of emergence was characteristic of a number of parasitic Hymenoptera in several families even though oviposition was limited to a 24h period. The spread was the result of differential rates of development in different stages; and which stage differed varied with the species.

Some solitary ectophagous species show a considerable adaptability with regard to the size of host individuals upon which development can be successfully completed. Noble found that Habrocytus cerealellae, when developing on small Sitotroga larvae, is able to pass through the final larval stage without feeding and to attain the adult stage. In such cases the larval stage was prolonged with resulting adults of minute size.

The second instar larvae of all species are of simple form, with the sensory and integumentary setae reduced in size; the latter are often absent. The nine pairs of spiracles occur on the last two thoracic and the first seven abdominal segments. In H. cerealellae, only the four pairs that persist from the first instar are open immediately after the molt, and the additional five, which are smaller, appear later in the stage. The larva of P. graminea is indistinctly segmented, and the head is much reduced, with the mandibles small, curved, and very widely spaced.

The full complement of five larval instars has been described for Eupteromalus nidulans, E. fulvipes Forbes, Dibrachoides dynastes, Pachycrepoideus dubius Ashm., S. micans, and Merisus destructor Say. Dibrachys cavus and H. cerealellae, both of which have been studied in detail, apparently have only four, and Habrocytus sp. discussed by Dustan has only three. Kutter described only two for Pirene graminea, though his prepupa shows distinctive characters representing presumably a third instar.

The fourth instar larva of S. mican is distinguished from other larvae of the family by a heavily sclerotized boring armature on the head. This consists of a transverse plate with a serrate edge situated immediately above the labrum and one or two heavy conical spines on the median line below the antennae.

The mature larvae of the different species are uniform in their characters and present no general distinguishing features. The mandibles are simple, and the integu­ment is smooth, with the sensory setae reduced in size. In H. cerealellae, there are three pairs of prominent spines at the end of the last abdominal segment. This species and Pseudocactolaccus asphondyliae, show pronounced intersegmental ridges dorsa11y. The tracheal system usually has nine pairs of spiracles, situated as on the second instar. However, Haviland (1922b) recorded 10 pairs for Asaphes vulgaris Wlk.; the first of these is situated on the intersegmental membrane between the first and second thoracic segments, and those following are on the third thoracic and the first eight abdominal segments. There is a vestigial tenth pair on the eighth abdominal segment in H. trypetae Thoms. The spiracles of S. micans first appear on the fourth instar, and rudimentary spiracular stalks are also present on the first thoracic and the eighth abdominal segments. Kutter's figure of the prepupa of Pirene graminea, which bears the external structures of the mature larva, shows the last segment produced into tubelike form and bearing two pairs of strong setae at the distal end. This tube is stated to be retractile.

Kearns describes an unusual development of the internal tracheal system in the endophagous first and second instar larvae of S. micans (Fig. 47C). Both instars possess the usual longitudinal trunks, with dorsal and ventral commissures at the anterior and posterior ends, respectively, and blunt spiracular stalks in the last two thoracic and the first eight abdominal segments. In addition, a pair of visceral tracheal trunks arise from the anterior commissure and extend over the dorsum of the intestine to the eighth abdomi­nal segment, where they unite. These visceral trunks were not detected in the third to fifth instar larvae. A comparable modification of the tracheal system was not known in any other hymenopterous larva in 1940 (Clausen 1940).

Another departure from the normal respiratory system is described by Dustan (1923) for the larva of Habrocytus sp. parasitic in Rogas pupae. His description of that of the mature larva is as follows: " Perhaps the most amazing thing about this parasite is its immense tracheal system which, as was said previously, almost fills the body cavity. It has a tracheal trunk running down each side of the body and spiracles that can be made out under the 4 mm. objective, which appear to be closed, however; but more unusual than all, it possesses myriads of tracheids packed into every conceivable part of the body. These tracheids are collected into bundles or areas which are held in place by a definite wall or membrane. Just inside the wall of each bundle we find a ring of tracheids, varying somewhat in size but alike in having extremely thin walls. All the space inside the tra­cheids is packed with blood corpuscles and plasma, so that each bundle really consists of a tracheal sheath, the inside of which instead of being hollow is filled full of blood.... These tra­cheids open at the hypodermal wall and in this way secure an abundant supply of oxygen from the blood stream of the host. This oxygen is then carried in the tracheal bundles to all parts of the parasite and distributed by the blood stream to the different organs and tissues."

Stenomalus micans Ol., 4th instar larvae, which are parasitic in larvae of Chlorops taeniopus Meig., bears a specialized boring apparatus on its head that is used to break up the internal organs of the host and to effect emergence through the hardened shell of the host larva, which has died just as it was undergoing pupation (Kearns 1931). No feeding occurs during the 5th larval stage, which is very short in duration. Parasitism by Stenomalus results not only in appearance changes of the host larva, but in its activity. Healthy larvae move downward in a barley stem and, prior to pupation, turn about and ascent to a point just below where the leaf leaves the stem. Reddish-brown puparia are then formed. Parasitized individuals do not make this position reversal, and partly formed puparia are colorless.

Normally pupation in Pteromalidae occurs in the cell, cocoon or other cavity in which the host resided. However, Eupteromalus nidulans forms a naked pupa in the web of its lepidopterous host. Nasonia vitripennis pupae retain the larval exuviae about the posterior portion of the abdomen, and this, adhering to the meconium, attaches the pupa to the host puparium wall. Enargopelte ovivora Ishii is one of the few Chalcidoidea showing a tendency toward normal cocoon formation (Ishii 1928). Mature larvae, of which there may be circa 10 in the egg chamber of Lecanium sp., spin individual, yellowish-brown cocoons.

In some species many individuals are able to develop on a single host. Martelli (1907) recorded 165 adults of Pteromalus puparum from a single pupa of the cabbage butterfly, and Picard (1922) reared 212 males from the same host and 47 Tritneptis klugii Ratz. (= P. nematicidus Pack.) have been secured from a cocoon of Lygaeonematus erichsonii Htg. (Hewett 1912). Roubaud reared 105 N. vitripennis from a single dipterous puparium. Such figures undoubtedly represent maximums for which food material was available. However, in most gregarious species development to maturity is possible even if only a portion of the available food material is utilized. The different species of Dibrachys usually develop in numbers of <10 on each host, and all the recorded species of Habrocytus are solitary. Muscidifurax raptorellus K. & L. has both solitary and gregarious races, the habit being under the control of polygenic loci (Legner 1987d, 1988a, 1989b, 1991). The gregarious races produce individuals of a characteristic size (Kogan & Legner 1970).

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Life Cycle

Pteromalids usually have short life cycles, averaging circa 3 weeks from egg to adult at room temperature. There was a minimum of 10 days recorded for Habrocytus cerealellae and Nasonia vitripennis. The females of many species require 1-2 days longer for development than do the males. The incubation of the egg requires from less than 1 day to 3 days, the larval stage 4-10 days and the pupal stage 4-14 days. A notable exception is E. ovivora, in which the egg, larval, and pupal stages take 7 days, 20 days and circa 11 months, respectively (Clausen 1940/1962).

The availability of suitable host stages influences the number of generations per year. Most species produce generation after generation as long as hosts are available, but some species are limited to a fixed number. E. ovivora has only one generation per year which corresponds to the host cycle. Pirene graminea and Stenomalus micans have two generations, as do their respective hosts. However, Aplastomorpha calandrae (Cotton 1923) and H. cerealellae are able to produce several generations to each one of the host. In these species there is no need for synchronization of the cycles of parasitoid and host, for they attack insects infesting stored grains which have all stages present continuously. Trineptis klugii has circa 6 generations each year on one brood of the host.

Most species that hibernate do so in the mature larval stage within the host cocoon, puparium or cell. But, Eupteromalus nidulans is found in the hibernation webs of the satin and brown-tail moths. E. ovivora, Rhopalicus suspensus Ratz., and Merisus febriculosus Gir. pass the winter in the pupal stage, while Dibrachoides dynastes and Pseudocatolaccus asphondyiiae Masi persist through the winter as adults. Other may pass winter as either mature larvae or adults.

A number of Pteromalidae are able to undergo long periods of inactivity as either larvae or adults when conditions are unfavorable. The relation of food to reproduction in Spintherus and Peridesmia was already noted, and it was shown that phasic castration in females may continue for a long time. This is one way of maintaining a species during periods of adverse conditions; another is larval diapause, such as is found in H. medicaginis Gahan and Nasonia vitripennis. In the former individuals have been observed to pass almost two years in the larval stage, as compared to the normal two weeks. Nasonia vitripennis may even pass several years in dipterous puparia when conditions are unfavorable (Clausen 1940/1962).

Adults live much longer than many other chalcidoid parasitoids. Species which normally pass the winter as adults are exceptionally hardy, and D. dynastes has been kept alive for >8 months at temperatures of 5-13°C. Species without diapause usually live 6-8 weeks.

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Sex Ratio & Parthenogenesis

Females predominate in ratios up to 30:1 in Habrocytus medicaginis. Clausen (1940) noted that ratios for N. vitripennis vary from 1:1 to 10:1. The normal ratio for P. puparum is circa 2:1; but George (1927) noted a seasonal variation, the ratio being 2.8:1 in springtime and 1.1:1 in autumn. In H. cerealellae, the field sex ratio is circa 3:2. Experimental determinations give an increasing proportion of male progeny toward the end of the life of females (Clausen 1940/1962; Legner & Gerling 1967), even in thelytokous populations (Legner 1987c). Griswold (1929) recorded an excess of males in the ratio of circa 3:1 in some rearings of Asaphes americana from aphids collected in glasshouses.

Extended studies in thelytoky have been done on Muscidifurax uniraptor Kogan & Legner, showing the presence of extranuclear influences (Legner 1985a,b; 1987b,c; 1988c). Certain bacteria have been found in the male and female reproductive tracts which are capable of inducing endomitosis in unfertilized eggs, thereby causing them to be diploid and female (E. F. Legner unpub. data, R. Stouthamer unpub. data).

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Cleoneminae (Pteromalidae)

The subfamily was once considered as a separate family, Cleonymidae. Pteromalidae now includes the former separate families, Cleonymidae, Miscogasteridae and Spalangiidae, which have been designated subfamilies Cleoneminae, Miscogasterinae and Spalangiinae, respectively. For the present, discussions of these various subfamilies will be separate because of considerable distinctness among them.

Three species for which some information is available are Schizonotus sieboldi Ratz. (Cushman 1917, Dowden 1939), S. paillotti F. & F. (Faure 1926) and Cheiropachys colon L. (Russo 1926, 1938).

Schizonotus sieboldi is gregarious and external on the pupae of Plagiodera versicolor Laich. and closely related chrysomalid beetles in the northeastern U.S. and Europe. Dowden (1939) indicated that it is an important factor in natural control of this host. Adult parasitoids occur in protected places and winter and attack the first brood of hosts in springtime. During oviposition the ovipositor is thrust beneath the pupa from the side, and one or more eggs are laid on the thorax between the appendages, although sometimes also on the abdomen or dorsum. Adult females feed upon host body fluids that exude from the puncture made in the dorsum after oviposition. Clausen (1940) commented that this is one of the few parasitic species that can develop externally upon exposed hosts, although the larvae are found between the body of the fixed host and the leaf, so that such conditions simulate the confined quarters of a burrow or cocoon.

Schizonotus paillotti differs from S. sieboldi in being hyperparasitic on some Lepidoptera through Apanteles in Europe. It is a solitary external parasitoid of the mature larva in the cocoon. Females feed on host body fluids prior to oviposition through a constructed feeding tube.

Solitary Cheiropachys colon parasitizes mature larvae of Scolytidae in Europe externally. Hosts are paralyzed at the time of oviposition, and the large egg is deposited on the body. Sex ratios favor females 5.5:1.

Immature Stages of Pteromalidae (Cleonyminae)

The eggs of Cleonymidae had been described for only the three species by 1940 (Clausen 1940). Those of S. paillotti and S. sieboldi are elongate-oval or somewhat cylindrical in outline, and that of C. colon (Fig. 48A) is narrowed at both ends, with the anterior and drawn out into stalk-like form and at times folded back upon the main body after deposition. In S. paillotti and C. colon, the chorion is clothed with minute spicules though sparsely so in the last named species, whereas S. sieboldi bears instead a fine reticulation on one side.

The first instar larvae of the family are hymenopteriform, with small sensory setae and the integumentary setae may be uniformly distributed or in bands at the segmental margins. The respiratory system is equipped with spiracles on the mesothorax and first three abdominal segments.

The second to fifth instar larvae present no distinctive characters. The sensory setae and integumentary spines are minute. Nine pairs of spiracles appear on the fifth instar, these being situated on the second and third thoracic and the first seven abdominal segments.

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Miscogasterinae (Pteromalidae)

The subfamily was once considered a separate family Miscogasteridae. Pteromalidae now also includes the former separate families, Cleonymidae, Miscogasteridae and Spalangiidae, which have been designated subfamilies Cleoneminae, Miscogasterinae and Spalangiinae, respectively. For the present, discussions of these various subfamilies will be separate because of considerable distinctness among them.

A relatively small family with species of Tomocera, Scutellista, Aphobetoideus and Anysis being essentially predators on the eggs of lecaniine Coccidae. Miscogaster is an internal parasitoid of the larvae of leaf-mining Agromyzidae, and Megorismus is parasitic in Aphididae, and several genera are known from Hymenoptera. Some species of Dinarmus are known as solitary external parasitoids of the larvae of Tephritidae. Host preferences are varied, and host relationships include a wide range extending from predation on eggs and larvae of other insects to true internal and external parasitism. Miscogasteridae are closely related to the Pteromalidae.

Scutellista cyanea Motsch. has been used extensively in biological control. This parasitoid was originally introduced from Italy to Louisiana in 1898 to combat Ceroplastes and from South Africa to California in 1901 for biological control of black scale, Saissetia oleae Bern. Establishment occurred in some areas, and although the parasitoids became abundant, there was very little reduction in the host population density because the parasitoid larvae did not consume the entire batch of eggs beneath the host and consequently a sufficient number of survivors remained to infest trees. In California S. cyanea has largely replaced Tomocera californica How., which had similar habits and which previously had effected about the same degree of natural control.

Biology & Behavior

Scutellista cyanea is predaceous on eggs of various lecaniine Coccidae contained in the cell beneath the parent female's body. When eggs are unavailable, the larva is able to develop as an external parasitoid of the female scale. Preferred hosts are Saissetia oleae and Ceroplastes rusci L., although occasionally Coccus and Phenacoccus, etc. are utilized.

During host selection the female shows a preference for mature females, usually those which have just laid a portion or all of their eggs. The scale is first examined with the antennae until the posterior arch is found, after which the position is reversed and the ovipositor is inserted by a backward thrust through the arch. Sometimes eggs are laid under scales from which all young have already emerged and also under those which have just completed the second molt and are without eggs. Normally the parasitoid eggs are found among those of the host, where they may be distinguished by their larger size and white color as compared to the pinkish host eggs. If no host eggs are present, the parasitoid egg adheres to the scale's ventral portion.

On hatching the young larva begins feeding on host eggs. At maturity a pupation cell is formed among the mass of empty eggshells and debris. The debris is matted together with small amounts of silk, which strands also bind the inner edge of the scale to the substratum. The meconium is case and pupation occurs. At emergence the adult parasitoid cuts a circular opening in the dorsum of the dead host, similar to but larger than those of true internal parasitoids. Old parasitized scales may adhere closely and remain on the tree longer than unparasitized scales. They may persist for 2-3 years.

The life cycle is about 41 days, of which 4-6 days are required for egg incubation, 15-21 days for the larval stage and 15-20 days for the pupa. Newly transformed adults may remain under the scale for several days before leaving.

Scutellista's seasonal cycle is correlated with the host. In areas of California where the host has a distinct annual cycle, the parasitoids are abundant only during June and July, for there is no suitable alternate host available in sufficient abundance to maintain a high density. Optimum conditions for the parasitoid require a continuous supply of maturing scales, condition which is approached only in coastal areas. There is no definite hibernation stage in California, and development continues, although at a reduced rate, through winter. In Italy there are circa 5 generations each year, the first being on Ceroplastes and the remaining four on Ceroplastes, Philippia and Saissetia.

On small Saissetia females, that can produce 500 eggs, a single parasitoid larva may consume the entire lot, thereby being able to halt reproduction. However, in large scales, which may deposit 2,500 or more eggs, only a portion can be consumed by a single parasitoid larva. Thus, control is considerable greater on small than large hosts (Clausen 1940/1962).

There are distinct biological forms which are not easily transferable from one host to the other. In Australia, the parasitoid attacks only Saissetia, while the African form is on Ceroplastes. The first introduction into the United States was of the wax-scale form from Italy to Louisiana, while the California introductions were of the black scale form from South Africa. Both of these hosts are heavily attacked in Italy, although it is not known if there are distinct parasitoid forms present.

Behavior of other Miscogasteridae attacking coccids is similar to that of Scutellista cyanea. Tomocera californica (Smith & Compere 1928) on the same host sometimes oviposits through the posterior arch and other times around the periphery of the scale. Like Scutellista the larva is able to develop as an external parasitoid of the female scale if eggs are unavailable. Aphobetoideus comperei Ashm. inserts the ovipositor underneath the lateral scale margin (Smith & Compere 1928).

Miscogaster sp. in France develops as a solitary internal parasitoid of the larvae of Agromyza mining the leaves of lucerne (alfalfa) (Parker & Thompson 1925). The ovipositor is inserted through the leaf surface and into the body cavity of the host. The tip of the egg stalk remains fixed in the puncture in the host integument, but the larva does not maintain a connection with it after hatching.

The behavior of immature stages of Systasis dasyneurae Mani differ in several respects from those of other Miscogasteridae by being predaceous on 2nd instar larvae of the midge, Dasyneura lini Barnes in linseed buds in India (Ahmad & Mani 1939). Eggs are deposited singly within the crumpled and unopened flower buds containing well developed midge larvae, although not always in their immediate vicinity. The newly hatched larva is active and in most cases quickly finds the midge larvae. The predators requires 3-4 midge larvae to complete development, but if more are present all are killed, although they are not completely consumed. Pupation is within the bud, and the cycle from egg to adult is 25-32 days at 18°C.

Immature Stages of Miscogasterinae

The ovarian eggs of the Miscogasteridae are of the two bodied type, but at deposi­tion the anterior body disappears and only a stalk or peduncle remains. In Scutellista (Fig. 49A), Miscogaster and Anysis, this stalk or peduncle is circa 1/2 the length of the egg body; but in Aphobetoideus (Fig. 49B) it is broad and stub like and in Tomocera nipple like and minute. The egg of Dinarmus dacicida Masi is ovate in form and lacks either a stalk or a peduncle.

The first instar larvae are hymenopteriform, with a variable number and arrange­ment of segmental spines. That of S. cyanea (Fig. 49C) bears no spines whatever, while Miscogaster sp. (Fig. 49D) has a complete ring of 30-40 heavy spines about each segment. In T. californica, there are only two pairs on each segment, whereas in Systasis dasyneurae three rows encircle each segment. Spiracles are found on the second and third thoracic and the second and third abdominal segments in Scutellista cyanea, on the second thoracic and first three abdominal segments in Anysis saissetiae, and on the second thoracic and first and fifth abdominal segments in T. californica. No spiracles are described or figured for Miscogaster sp., which is further distinguished from others of the family by the bilobed form of the last abdominal segment, each lobe terminating in a heavy spine.

The intermediate instar larvae have not been described for any species, nor has the number of stages been determined as of 1940 (Clausen 1940).

The mature larva has been described only for S. cyanea. The cuticular spines are minute or lacking and the respiratory system now possesses nine pairs of spiracles, situated on the last two thoracic and the first seven abdominal segments.

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Spalangiinae (Pteromalidae)

This subfamily was originally a separate family Spalangiidae. Pteromalidae now also includes the former separate families, Cleonymidae, Miscogasteridae and Spalangiidae, which have been designated subfamilies Cleoneminae, Miscogasterinae and Spalangiinae, respectively. For the present, discussions of these various subfamilies will be separate because of considerable distinctness among them.

Legner (unpub. data) working with parasitoids of synanthropic Diptera has observed what he regards as a higher degree of intelligence among species of Spalangia than of various pteromalid parasitoids, as manifested by more intense searching of the host's environment and examination of the host prior to parasitization. Also, during numerous laboratory experiments with various species of this genus, they have shown a degree of learning toward the ultimate goal of escape from the experimental environment. After repeated handling their ability to feign death, for example, is remarkable, which frequently results in their escape from the observer.

There are only a few genera, of which Spalangia is the most commonly encountered. Richardson (1913) listed six species from dipterous hosts, one from Lepidoptera and two with myrmecophilous habits. The recording from the lepidopterous host is probably in error, for the species concerned, S. nigra Latr, has been frequently recorded from housefly puparia (Bou…ek 1963). Silvestri (1914) recorded several species from Trypetidae in West Africa. Those which attack Diptera utilize puparia and are solitary and external in habit. Clausen (1940) noted that these are parasitoids of dipterous pupae and consequently are considered hyperparasitoids only when the particular host species that they attack are themselves of parasitic habit, although S drosophilae Ashm., attacking dung-infesting Diptera, is recorded as attacking Alysia and Psilodora, which are primary parasitoids of the same hosts. Entomophagous Diptera which form their puparia on or near the soil surface are frequently attacked by Spalangiidae. Cerocephala develops on larvae and pupae of the coleopterous families Scolytidae, Curculionidae, etc. (Clausen 1940/1962).

Spalangiidae are valuable in the natural control of synanthropic Diptera both naturally and through artificial field inundation. Lindquist (1936) recorded up to 64% parasitization of dung-infesting Diptera, mainly by Spalangia muscidarum var. stomoxysiae Gir.

Biology and Behavior

Richardson (1913) did an extensive study on S. nigroaenea Curtis (= S. muscidarum) as a solitary parasitoid of the pupae of housefly, Musca domestica L. In oviposition, the female crawls over the host puparium, examines it carefully with the antennae, and then inserts the ovipositor through the puparial wall, usually in the posterior half. The body of the larva or pupa within the puparium is not penetrated, and the egg is placed externally.

The 1st instar larva is very active and capable of extended movement over the surface of the host, which is for the purpose of finding a suitable feeding point, which usually proves to be the dorsum or dorsolateral areas of the abdomen (Gerling & Legner 1968). The pupal integument is much thinner at these points and is more easily punctured than elsewhere. The 2nd and 3rd instar larvae are relatively more fixed in their feeding positions in S. cameroni Perkins (Gerling & Legner 1968). When feeding is complete, the mature larva moves toward the anterior end of the puparium, casts its meconium and then pupates. The adult emerges through a hole cut in the anterior end of the puparium (Clausen 1940/1962).

An account of S. nigroaenea as a parasitoid of stablefly, Stomoxys calcitrans L. was given by Pinkus (1913), which differs in several respects from that by Richardson. Oviposition took place in the anterior portion of the puparium, usually through a suture. The female was able to detect prior parasitization and would not deposit a second egg on a host already bearing one. Many of the pupae attacked died, even though no egg was deposited, which would indicate that the body had been penetrated by the ovipositor. The adults mate soon after emergence, and females are able to deposit eggs the same day.

A minimum life cycle under cool laboratory conditions was found to be circa 88 days, but under warmer summer conditions outdoors the cycle is less than half this duration. Hibernation was thought to take place in any immature stage, and development progressed at any time that the temperature became higher again.

Spalangia parasitizing the pupae of Lyperosia were studied by Handschen (1932, 1934). These were S. sundaica Graham of Java and S. orientalis Graham from Australia. S. sundaica deposited an average of 160-170 eggs during a 4-weeks period. The cycle from egg to adult was completed in 18-21 days, and males emerged two days earlier than females. Adults were attracted to dung in which the hosts develop. S. orientalis had the same general habits and life cycle but produced an average of only 85 eggs during 15 days. These two "species" were hybridized in an effort to produce a more effective "race" that was better adapted to Australian conditions. Female S. orientalis when mated with male S. sundaica produced progeny more prolific than either parent form, the average egg deposition being 240 in 32 days. The reverse cross produced 100 eggs during 10 days. The fact that the hybrids were fertile and highly fecund, it is indicative that races instead of species had been studied. Yet Bou…ek (1963) considered S. orientalis a synonym of S. endius Walk. and S. sundaica a synonym of S. nigroaenea Curtis. During three decades of research on Spalangia and related genera, Legner (unpub. data) has never obtained hybrids between S. cameroni and S. nigroaenea. Studies with Australian Spalangia nevertheless have raised some interesting questions, as for example the reproductive isolation of a race of S. endius secured from the southeastern portion of the continent from that of morphologically indistinguishable isolates from North America. A morphologically and biologically distinct race from New Zealand, however, although isolated from the Australian isolate fully interbred with North American S. endius (Legner 1983).

In Cerocephala cornigera Westw., parasitoid of scolytid larvae and pupae, the female first paralyzes the host and then places an egg either directly on it or in its immediate vicinity. The ovipositor is usually inserted into the entrance of the host's oviposition tunnel.

Adult feeding habits in the family were studied by Lindquist (1936) who found that Spalangia muscidarum var. stomoxysiae paid little attention to artificial foods, and the length of life when confined with puparia suggested host feeding. Parker & Thompson (1925) found such feeding in S. nigra Latr, where they noted the construction of a feeding tube.

Life cycles in Spalangiidae are short, ranging from 17 days in S. muscidarum var. stomoxysiae and S. drosophilae to 25-30 days in C. cornigera. More than one generation is produced each year, and winter is passed in the mature larval stage, although Richardson found that S. muscidarum is in the pupal stage during winter.

The developmental life history of Spalangia cameroni Perkins was presented by Gerling & Legner (1968), with observations on physiology of ovum formation, and sperm translocation through the male reproductive system. Pertinent aspects treated in detail were host-feeding and selection, oviposition, superparasitization, length of developmental stages, oocyte development, ovisorption and sperm activation. Particularly interesting were the interinvolvement of host-feeding and oviposition, the high moisture requirement for embryonic development and the 100+ feeding punctures made by a larva while feeding ectophagously on the host pupa encased in the puparium. There was a prolongation of female pupal development with respect to the male, a deposition of partially resorbed eggs, two chambers in the seminal vesicle, and a short duration of testes function.

The sex ratio varies with environmental conditions (Legner 1967a,b; 1969, 1979a,b; Legner & Gerling 1967), but females tend to predominate in a ratio of 2:1 in S. muscidarum var. stomoxysiae. There has been no thelytoky discovered in this family.

Immature Stages of Spalangiinae

Clausen (1940) noted that the 1st instar larva is very active and capable of extended movement over the surface of the body of the host pupa. This is for the purpose of finding a suitable point for feeding, which varies, but usually is around the dorsum or dorsolateral areas of the abdomen. The skin of the pupa is much thinner at these points and more easily punctured than elsewhere. The 2nd and 3rd instar larvae have a fixed feeding position.

The eggs of Spalangia muscidarum and S. nigra are elongate ovate in outline and broader at the anterior end, which bears a nipple like protuberance. That of Cerocephala is of similar form except that the anterior protuberance is lacking.

The first instar larvae are hymenopteriform and elongate oval in outline and have a relatively large head. In S. nigra (Parker, 1924), each body segment bears a band of minute setae at the anterior margin. An open tracheal system is found in S. nigra with the spiracles occurring on the second thoracic segment, or on the membrane between the first and second, and on the first three abdominal segments (Fig. 50A). Richardson emphasized that not only does the first instar larva of S. muscidarum lack spiracles, but the intermediate and mature larvae are likewise apneustic.

The number of larval instars in the family is uncertain, with only three mentioned for S. muscidarum and four for S. nigra. The second (Fig. 50B) and third instar larvae of the latter species bear nine pairs of spiracles, situated on the second and third thoracic and the first seven abdominal segments.

The mature larvae of the genus Spalangia (Fig. 50C) are distinguished by the possession of distinct conical protuberances or tubercles at each dorsolateral margin of the first eight abdominal segments. A minute pair is found on the first thoracic segment. These tubercles have not been noted upon larvae of other genera. They are considered by Richardson to have neither an ambulatory nor sensory function, but appear to relate to prepupal growth. The mature larva of C. cornigera is more elongated than that of Spalangia, and each body segment bears four pairs of setae, those of the last segment being longest.

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