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Brachymeria minuta (Linnaeus, 1767) |
Chalcis biguttata Spinola, 1808
Chalcis myrifex (Sulzer, 1776)
Chalcis sispes (Linnaeus, 1761)
Haltichella rufipes (Olivier, 1790)
Spilochalcis xanthostigma Thomson, 1876
Chalcidids are a moderately sized family with circa 115 valid genera and 1415 species by 1993. They are cosmopolitan but are most abundant in the tropics, particularly in South America. Important morphological characters include 13-segmented antennae, with 1 or 2 ring segments and with club segments not markedly different from the funicle. The hind coxae are large and cylindrical. The hind femora are greatly enlarged, their ventral surface bearing denticles or spines. The hind tibiae are arched. They have well developed parapsidal sutures and a head and thorax that is frequently coarsely punctate.
Most chalcidids are primary, larval, endoparasitoids. All are solitary. Some ectoparasitic and hyperparasitic species are known. There is a wide host range. They are principally parasitoids of Lepidoptera, although Coleoptera and Diptera also are attacked commonly. Hyperparasitic species attack tachinid and braconid primary parasitoids. The family has not been used much in biological control. One species of Brachymeria has been introduced to the United States for gypsy moth control, with moderate success.
This family is cosmopolitan in distribution and is represented most commonly by the genus Brachymeria. Many of the species are relatively large in size and bear conspicuous markings. As primary parasitoids, they may be found attacking Lepidoptera, Diptera (Sarcophagidae & related families), and Coleoptera. The genus Dirhinus is a common parasitoid of fruit flies of the family Trypetidae in tropical regions. In the hyperparasitic role, many are found to attack Diptera (Tachinidae, etc.) and ichneumonoid Hymenoptera. Species of Spilochalcis are frequently reared from the cocoons of the latter. All known species are solitary in habit and, with the exception of Euchalcidia and Dirhinus, develop internally. The different species of the family seem to have a very wide range of hosts. Thus, B. intermedia Nees attacks and will develop in almost any naked lepidopterous pupa, and B. compsilurae Cwf. and B. fonscolombei Duf. exhibit a similar broad preference with respect to sarcophagid and other pupae. As for natural control of insect pests, the benefits resulting from the reduction of blowflies and related forms of Lepidoptera are fully offset by the losses from the hyperparasitic forms, and the family as a whole cannot be considered beneficial. Few species have been utilized in biological control, and none has shown any marked degree of effectiveness.
Gibson (1993) noted that in the Chalcididae, the body was without a metallic luster (except for Notaspidium). They are mainly black or brownish to entirely yellow or reddish. The head and mesosoma are heavily sclerotized, usually coarsely punctate at least in part. The head dorsally sometimes has a projection (horn) between the scrobal depression and each eye. The gena is carinate or ridged. Antennae are inserted below or above the level of ventral ye margin. The flagellum is shorter than the length of the eye and with 5-7 segments or conspicuously longer then the eye and with 9-11 segments, the first segment ring-like or not. The pronotum has a quadrate to transverse subrectangular collar (posterior margin often conspicuously curved inward) or rarely almost linear in dorsal view, but with lateral margin straight and not extending to the tegula (cf. Leucospidae). The prepectus is small, often difficult to distinguish. The mesopleuron has a shallow femoral depression over most of its height. They are fully winged, with the forewing not folded lengthwise and with venation sometimes reduced to oblong spot at the apex of the submarginal vein, but usually with marginal and stigmal veins distinct, the marginal vein usually longer than the stigmal. The postmarginal vein is absent or long. Tarsi have 5 tarsomeres. The metacoxa is long and in cross section subcircular to very large and subtriangular. The metafemur is large, compressed, and ventrally serrated or dentate over at least the apical 1/3rd. The metatibia is usually distinctly curved, either truncate with 2 apical spurs or obliquely pointed with 1 spur or none. The metasoma has either a transverse or long and slender petiole that is rarely inserted high on the propodeum adjacent to the metanotum or longitudinally carinate. Postpetiolar terga are separate. The ovipositor sheath protrudes only slightly (Gibson 1993).
This family is widely distributed, with circa 195 nominal genera and 1,875 nominal species. They are easily distinguished, even with inclusion of the bizarre subfamily Smicromorphinae, but Chalcididae could well be paraphyletic relative to Leucospidae (Gibson 1993). Chalcidids are primary parasitoids or hyperparasitoids, mostly of Lepidoptera (primarily young pupae) and Diptera (primarily of mature larvae), though some parasitize other Hymenoptera or Coleoptera, and a few are known from a wide variety of other insect hosts. The modified hind legs seem to have several functions, at least in females. Females of some species retain the host between the toothed femur and curved tibia during oviposition, while others stand upright on the hind legs so that the front and middle legs are free to manipulate the host. Females are also known to use the hind legs in back-to-back fighting, and females of Lasiochalcidia igiliensis Masi use their hind legs to hold apart the mandibles of ant-lion larvae (Neuroptera: Myrmeliontidae) while ovipositing into the membrane between the head and thorax.
Bou…ek (1988a) keyed the subfamilies known from the Australasian region and listed published keys to genera from other regions. Delvare & Bou…ek (1992) revised the genera of the family and the species of the Chalcidini from the New World.
NEARCTIC (CANADA).-- Yoshimoto (1984) noted that "Adults of the family Chalcididae are usually black, sometimes reddish or with pale markings, robust, and large. Members of this family can be identified by the following characters: Body highly sclerotized, not metallic in color, with head and thorax coarsely punctate and thorax having distinct notauli. Hind coxae enlarged; hind femora swollen and toothed ventrally; hind tibia curved as in Leucospidae, Chalcedectinae (Pteromalidae), and Podagrionini, Monodontomerinae (Torymidae). Gaster not punctate. Prepectus small, inconspicuous. Ovipositor barely protruding from body."
"The included species are largely parasitic on pupae of Lepidoptera or on maggots and puparia of Diptera, though they have also been reared from Hymenoptera, Orthoptera, Coleoptera and Neuroptera."
"Masi (1916, 1929a, 1929b) published a series of papers on this family. Habu (1960) has given an excellent synopsis of the family in Japan, and Bou…ek (1952) made a comprehensive study of the European Chalcididae with synonymies and keys to genera and species."
Yoshimoto (1984) provided keys to subfamilies of Chalcididae: Chalcidinae, Brachymeriinae, Halticellinae and Dirhininae. In Canada, Chalcidinae are represented by three genera: Chalcis Fabricius, Ceratosmicra Ashmead and Spilochalcis Thompson. Brachymeriinae in Canada is represented by three genera: Phasgonophora Westood, Trigonura Sichel, and Brachymeria Westwood. The Haltichellinae is represented by Haltichella xanticles (Walker) from Québec. There is one genus, Dirhinus of the Dirhininae in North America, but it does not occur in Canada.
These are distinguished by a head with frons somewhat flattened; antennae inserted at or above level of ventral eye margin; margin vein touches wing margin; hind tibia arcuate, ventroapically forming sharp projection; mid tibia have a single apical spur (Yoshimoto 1984). There are three genera in Canada, Phasgonophora Westwood, Trigonura Sichel, and Brachymeria Westwood. Burks (1959, 1960) revised the last two genera, respectively.
The species are common and widely distributed throughout the world. Species of Brachymeria are primary or secondary parasitoids of Lepidoptera and Diptera; those of the other two Canadian genera, Trigonura and Phasgonophora, are though to be primary parasitoids of buprestid and scolytid beetles in wood or under bark (Burks 1959).
These are distinguished from other species of the family by the antennae being inserted at the middle of the frons; hind tibia are arcuate, with one weak spur; and the petiolate gaster. Canadian Chalcidinae are represented by genera Chalcis Fab., Ceratosmicra Ashmead, and Spilochalcis Thomson (Yoshimoto 1984). Keys to 5 genera and 49 North American species are in Burks (1940). Burks (1979) listed 49 genera and 54 species; and he included Xanthomelanus Ashmead of the neotropics. Spilochalcis is widely distributed in the Nearctic (Yoshimoto 1984).
The subfamily is distinguished by an elongated body, subcylindrical, or dorsally somewhat depressed; frons prolonged into two hornlike projections, with scrobes deeply excavated; elongated mandibles, with 2-3 short teeth; genae without malar groove; antennae inserted below level of posterior eye margin; fore wing with rudimentary postmarginal and stigmal veins; propodeum horizontal, flat, with typical cuplike cavity, or cell, with regular or irregular formation of ridges; hind tibia prolonged into sharp spinelike projection, with strong spur; gastral petiole often transverse, frequently with longitudinal ridges; gaster without coarse punctures except strongly striate area behind petiole (Yoshimoto 1984).
North American species are represented by the single genus Dirhinus Dalman. It is not recorded from Canada, but is known as far north as Illinois, in the United States.
Burks (1947) revised the North American Dirhinus spp. Bou…ek and Narendran (1981) revised the Indian species of Dirhinus with a key and synonymy. The species are parasitic on pupae of Tephritidae, Calliphoridae, Sarcophagidae and Muscidae (Yoshimoto 1984).
These are distinguished by a head that is usually wider than the thorax, without horns on frons dorsally; antennae inserted below ventral eye margin; preorbital carina along eye margins distinct, except in Hockeria Walker; frons flat, with scrobe forming deep depression with indistinct margins; marginal vein touching wing margin; apex of outer ventral edge of hind femur densely pectinate with small teeth; apex of tibia truncate with 2 apical spurs; a short petiole (Yoshimoto 1984).
Haltichellinae are represented by three genera in North America. The only Canadian record is Haltichella xanticles (Walker), from Québec.
The Haltichellinae of France was revised by Steffan (1951, 1953). Habu (1960) revised those of Japan, providing keys to genera and species. Species parasitize Lepidoptera, Neuroptera, Coleoptera and Hymenoptera (Yoshimoto 1984).
PALEARCTIC (EUROPEAN former USSR).-- Nikol'skaya (1978/1987), as translated from the Russian, described this family as "Large chalcids; up to 10 to 12 mm long and rarely less than 3.0 mm. Body black, sometimes light or dark brown, either with yellow or orange spots. Head and thorax usually covered with large and more or less dense punctation. Antennae with 11 to 13 segments. Pronotum transverse. Hind coxae cylindrical. Larvae endoparasites (primary and secondary) of Lepidoptera, Diptera, beetles, and some stem sawflies and antlions. More than 100 genera with 1,200 species; in the Soviet Union, 23 genera with 90 species; in the European part of the USSR, 20 genera with up to 50 species."
AFRICA.-- Prinsloo (1980) noted that because of the distinct shape of the hind legs and relative large body size, Chalcididae are probably one of the better known chalcidoid families. His discussion continues as follows:
Relationship & Diagnosis.-- "The Chalcididae is easily separated from most other families of the Chalcidoidea by the large, swollen hind femur which is ventrally toothed. There are, however, a few other groups, e.g., the Leucospidae, Monodontomerinae (Torymidae) and Chalcidectinae (Pteromalidae) which have similar hind legs, but the Chalcididae differs from all these groups by a combination of characters... The chalcidids are most closely allied to the leucospids, and in the past these two groups were placed in the same family."
"Medium to large chalcidoids; body often robust, the head and thorax coarsely sculptured or pitted; colour often black, or blackish, sometimes with yellowish to reddish markings; body without metallic refringence; thorax with well defined parapsidal sulci, the scutellum sometimes with apical processes; fore wings always developed; antenna thirteen-segmented in the female, sometimes with large ring-segments, the club often not differentiated from the funicle; hind leg with femur greatly swollen, its ventral margin toothed, the hind tibia correspondingly arched; tarsi five-segmented; abdomen sometimes distinctly petiolate."
Biology.-- "Chalcidids are usually internal primary or sometimes secondary parasitoids which attack the larvae or pupae of a large variety of insects, with a preference for Lepidoptera and Diptera. The species of Dirhinus, one of the few chalcidid genera which is ectoparasitic, are common parasitoids of fruit flies, and some species have been used in biological control programmes against these injurious insects. Many species of Brachymeria attack the pupae of a number of important Lepidoptera pests, such as Anomis flava (F.), Tortix capensana (Walker), Plutella spp. and Plusia spp., but others are also primary or secondary parasitoids of Diptera. Peltochalcidia is also a hyperparasitoid, and P. capensis Steffan attacks the braconid wasp, Macrocentrus maraisi Nixon, a primary parasitoid of the Karoo caterpillar Loxostege frustalis Zeller. Species of Hockeria are known to be parasitic in the pupae of saturniid moths of economic importance. A few chalcidids parasitize xylophagous beetles, and Hybothorax and Lasiochalcidia are unusual in that they attack the larvae of ant lions."
African Chalcididae.-- "A fair number of genera and species have been described from this region, and especially from Central Africa, but many of these will prove to be synonymous or incorrectly placed once the family is studied intensively, and it is therefore difficult to estimate the actual number of valid species presently known from Africa."
"The family may be divided into five subfamilies: Dirhininae, Epitraninae, Chalcidinae, Brachymeriinae and Haltichellinae. The Dirhininae, of which Dirhinus is the most common genus, is characterized by the head which has the frons projecting as two strongly developed horns. The Epitraninae is characterized by the hind tibia which is grooved in the apical half to receive the hind tibia. All the species in Africa probably belong to the genus Epitranus, the species of which are relatively small, the body slender, reddish in colour, and the abdomen with a long petiole. Like the Epitraninae, the petiole is elongate in the species of Chalcidinae, but the hind tibia is not grooved. Not much is known about the genera of this subfamily in our region. The Brachymeriinae comprises a few genera of which Brachymeria is well represented in Africa. The species of this genus are stout-bodied with short petioles, the legs always with white, yellowish or reddish markings. The Brachymeriinae are easily separated from the Haltichellinae by the obliquely truncate apex of the hind tibia which terminates in a single spur. Hockeria is a relatively well known genus of the Haltichellinae in which the fore wing is often infuscated, the scutellum terminating apically in two blunt teeth."
INDIA & ENVIRONS.-- Narendran (1988) noted that the family Chalcididae comprises medium to large chalcids whose hind femur is greatly modified into a swollen structure. "These chalcids are important and interesting, but also difficult parasitic insects to study taxonomically (Bou…ek 1951). Many species of this family are primary parasites (occasionally hyperparasites) of moths and butterflies. Other insects such as flies, beetles, wasps and bugs are also attacked. Even the ants and ant-lions fall prey to some of these chalcidids."
"Unfortunately, there is much confusion concerning the systematics of many genera of the Oriental Chalcididae and particularly of the Indian fauna despite some extensive attempts to improve our knowledge on some genera by Bou…ek (1982), Bou…ek & Narendran (1981) and Joseph, Narendran & Joy (1973). In the present paper I have recognized 30 genera as representing the family in India and the adjacent countries. Though more than 170 species are reported here as valid, some of these may eventually prove to be synonymous when my planned revisional studies on the family are completed."
Historical Review.-- "The study of chalcidids may be said to have begun well before 200 years ago when Linnaeus discovered and reported a few species such as Sphex sispes (Chalcis sispes), Vespa minuta (Brachymeria minuta) etc. Linnaeus was followed by Fabricius who was the first to coin the name Chalcis. Later, the names of Walker, Westwood, Dalla Torre, Dalman, Spinola, Haliday, Saunders, Motschulsky, Foerster, Cresson, Klug and Kirby stand out prominent among the early students of this group. The unfortunate fact is that the types of some of the species described by these authors either do not exist today (Bou…ek 1951) or it is not possible to find them today."
"Since the monumental work on the classification of Chalcidoidea by Ashmead (1904), our knowledge of the family has been greatly enhanced by the studies of Cameron, Crawford, Schmitz, Waterston, Girault, Gahan, Ruschka and Masi. During the recent years our knowledge on the family has been greatly enriched by the studies of Bou…ek (world fauna), Steffan (Palaearctic and Ethiopian fauna), Burks (Nearctic fauna), Erdös (Hungarian fauna), Habu (Japanese fauna), Nikol'skaya (Russian fauna), Mani and his students and Narendran (Indian fauna)."
"Contributions to the knowledge of Indian Chalcididae have been made in recent years by Gahan (1930, 1942), Waterston (1922), Masi (1927, 1929), Mani (1935-1938), Mani and his students (1972-1974), Joseph et al. (1973), Narendran (1976-1984), Bou…ek (1982), Bou…ek & Narendran (1981) and Husain & Agarwal (1981-1982)."
Classification.-- Narendran (1988) noted that the family Chalcididae was divided into the following six subfamilies (Schmitza 1946, narendran 1984a) and tribes: Brachymeriinae (Brachymeriini, Cratocentriini, Phasganophorini); Haltichellinae (Haltichellini, Hybothoracini); Chalcidinae; Epitraninae; Dirhininae (Dirhinini, Aplorhinini); and Smicromorphinae.
AUSTRALASIA.-- Bou…ek (1988) stated that "The present scientific name for the chalcidoid wasps is derived from Chalcis Fabricius and the group name was first formally established by Latreille (1817: 473). His proposal followed a suggestion by Spinola (1811: 146): "si l'on la juge nècessaire, la famille des diplolèpaires sera celle des chalcidiens, nom qui lui conviendra d'autant plus que cette famille rèpond presque entiérement au genre chalcis de M. Jurine." Before that time the groups in which all described chalcids were classified were called 'Cynipseres' and Diplolepaires,' both based on nominal genera which now belong to the superfamily Cynipoidea. latreille's name Chalcidites, emended to Chalcidide, was adopted by most subsequent authors (except notably by Nees, 1834, and Thomson, 1976 and 1878), especially when the group was upgraded to the superfamily by Ashmead (1897a, 1897b, 1904a). Walker (1834: 20) was the first to call it family Chalcididae in the present sense."
"The species of Chalcididae are relatively easily recognisable by the enlarged hind femora bearing a variety of teeth on the ventral edge, combined with the strong punctation of the thorax and a sharp carina bordering the genae posteriorly. The toothed and enlarged hind femora also occur in a few genera of four other families: Agaonidae, Torymidae, Pteromalidae and Eulophidae, but in these groups the thoracic sculpture and genae are different. The Australian species vary from 1.5 mm to about 16 mm in length, are mostly black, only rarely with some parts red or yellow (Smicromorpha sometimes wholly yellow) or with a very slight metallic tinge."
"In the last 50 years the genera of the family were keyed out in only a few regions of the world. The key to the African genera by Schmitz (1946) is already rather obsolete but the keys to the European genera by Bou…ek (1952; and in Peck, Bou…ek & Hoffer, 1964), to Haltichellinae by Steffan (in 3 parts, 1951-1953), to the Palaearctic genera by Nikolskaya (1960), Japanese genera by Habu (1960, 1962), and most recently to the Indian genera by Narendran (1984a and 1985) are still useful."
Biology.-- "All species develop as parasites on various other insects, mainly in their pupae. Due to the relatively large size of the body chalcidids are mostly solitary or slightly gregarious, but up to 50 specimens of some Brachymeria species may emerge from one large moth pupa. Most species attack Lepidoptera, the others attack particularly Coleoptera (mainly Chrysomelidae, with larvae on foliage as are caterpillars), Diptera, Neuroptera and Hymenoptera. One extralimital Hockeria was reared from a free-living Mengenilla, Strepsiptera. As pupal parasites certain species are hyperparasitic via the primary dipterous or hymenopterous parasites, some others only occasionally so (facultative hyperparasites). Hyperparasitic species are found in the genera Antrocephalus, Proconura, Notaspidiella and Brachymeria. Some very primitive genera, especially the Phasgonophorini and Cratocentrini, develop as parasites of wood-boring beetles. Several other genera include only species attacking particular groups, for instance species of Uga parasitise epilachnine beetles (Coccinellidae), those of the extralimital Lasiochalcidia antlion larvae, those of Smicromorpha ants of the genus Oecophylla, those of Dirhinus the puparia of brachycerous Diptera, and those of Chalcis the Stratiomyiidae (Diptera). The North-American Chalcis species oviposit into the eggs of stratiomyids, whilst two European species attack stratiomyid larvae."
"The distribution of the family is worldwide, but generally only a few species reach cold regions. The present number of strictly Australian genera is 21, with 176 species considered as probably valid, but another 9 genera are included here from New Guinea and the eastern parts of the Oriental region. The estimated number of valid genera of the world is about 70. The family is subdivided into five subfamilies, all represented in the region: Haltichellinae, Epitraninae, Dirhininae, Chalcidinae and Smicromorphinae. The former subfamily Brachymeriinae is here classificed as the tribe Brachymeriini of the subfamily Chalcidinae."
"Apart from the treated genera, two further ones were placed wrongly as Chalcididae by Girault: Chrysochalcissa Girault and Neochalcissa Girault. The former genus now belongs to Torymidae (Monodontomerinae), the latter to Pteromalidae (Ormocerinae). The generically transferred species are cross-referred both under the original genus and the present one, except in two large genera: Antrocephalus,, most species of which were originally placed under Stomatoceras, and Brachymeria, the numerous species of which were described by Girault, and others, under Chalcis."
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The genus Brachymeria has been most studied. Informative accounts are on B. femorata Panz. (Faure 1926; Kamal 1938a), B. intermedia Nees (Dowden 1935), B. fonscolombei Duf. (H. L. Parker 1923, Roberts 1933), B. compsilurae Cwf. (Dowden 1935) and Euchalcidia caryobori Hanna (Hanna 1934). Generally these species cover the range of host preferences and relationships of the family (Clausen 1940/1962).
Adults develop in lepidopterous pupae and emerge by biting away a hole at the anterior end, in a wing pad, or at the middle of the dorsum of the pupal shell, whereas those in puparia cut away the anterior end. Mating takes place very shortly after emergence, and the gestation period is usually 2-3 days, although B. fonscolombei was found to be able to deposit eggs within three hrs after emergence, and female progeny were secured from those deposited only 8-9 hrs thereafter.
Adults of species attacking carrion-infesting hosts are believed to derive a part of their food from the meat juices, and feeding on host fluids has been observed only in B. intermedia and E. caryobori, where it followed oviposition (Clausen 1940/1962).
Little variation exists in host stages attacked by species with similar preferences. Therefore, the parasitoids of Lepidoptera oviposit in young pupae, those attacking Diptera oviposit in the mature larvae, and Euchalcidia parasitizes either mature larvae or pupae of its bruchid host. B. compsilurae oviposits in tachinid larvae while they are still within the dead bodies of their lepidopterous hosts, and B. dalmani Thoms. has the unusual habit, for the family, of attacking living locusts and ovipositing in the parasitic maggots contained in their bodies (Olsaufiev 1929). Spilochalcis pallens Cress. oviposits directly in ichneumonoid cocoons. Dirhinus giffardi Silv. attacks the pupal stage of the fruit fly, rather than the mature larva.
The oviposition stimulus for hyperparasitic and scavengerous species is usually not provided directly by the primary host. Females of B. fonscolombei are strongly attracted to maggots freshly dipped in meat juices, and oviposition is readily secured in droplets of these juices even in the absence of maggots. The females of B. compsilurae are particularly attracted to dead lepidopterous larvae or pupae containing tachinid maggots, but free individuals of the latter are avoided. They must be within a dead or dying host. The liquid excretions of the maggots themselves are particularly attractive to the females, and they will try to oviposit in droplets of it.
Most species of Chalcididae have a low reproductive capacity. Dowden found that the ovaries of B. compsilurae comprise only 12 ovarioles and that only a single egg attains maturity in each at one time, suggesting a maximum of 12 eggs/day. B. intermedia has only 6 ovarioles with a correspondingly lower capacity. Kamal indicated that circa 180 eggs, deposited over a period of 60-70 days, is the maximum for B. femorata. B. fonscolombei has a much higher capacity; Roberts mentioned finding 177 mature eggs in one female, although a maximum of only 80 progeny was obtained. Euchalcidia caryobori deposited up to 220 eggs, with an average of 102 for a series of females, at the rate of circa 6 per day.
Adults are relatively long-lived in most species, with the exception of B. fonscolombei, which lives an average of circa 11 days at summer temperatures. B. compsilurae and E. caryobori survive for circa 6 weeks, while B. femorata and B. intermedia survive the winter and a considerable portion of the following season. Silvestri noted that D. giffardi adults lived for at least 5 months (Clausen 1940/1962).
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The cycle from egg to adult in those species having one complete generation or more during summer, ranges from 14 days in Spilochalcis pallens to 25 days in B. compsilurae, under optimum conditions. In several species the female requires 2 days longer than the male to complete its cycle.
Only adult females hibernate in B. femorata and B. intermedia, which parasitize Lepidoptera. In the latter, a portion of the females of the early broods may also carry over the winter. The species of this genus that attack Diptera pass the winter as mature larvae in the puparia (Clausen 1940/1962).
The habits and availability of hosts determine the number of generations produced each year. B. compsilurae has only one generation in Sturmia scutellata R.D., while 2-3 develop in Compsilura concinnata L. B. fonscolombei is estimated to have circa 8 in blowfly larvae, of which host there is a supply available at all times during the season. B. intermedia may have two generations and a partial third by utilizing several host species. Spilochalcis pallens, a hyperparasitoid of Laphygma frugiperda S. & A. through Meteorus and Apanteles, has several generations because the primary parasitoids are available over a prolonged period.
Sex Ratio & Parthenogenesis.--Sexes seem to occur in about equal number, based on current information. B. compsilurae, B. intermedia, B. fonscolombei, S. pallens and E. caryobori produce only male progeny from virgin females. Hanna (1935) studying the effect of low temperatures on the fertility of E. caryobori, found that the exposure of pupae to subnormal temperatures results in a shrinkage of female ovarioles, a marked reduction in egg production, and a high male biased sex ratio. Males are more readily affected by adverse temperatures than females, and male progeny of females subjected to such temperatures while in the pupal stage show a high incidence of sterility (Clausen 1940/1962).
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The eggs of the majority of species of the family are elongated and broadest at the anterior end, with both ends smoothly rounded, and the length is four to six times the maximum width. The micropylar area is represented by a small, slightly roughened area. In B. fonscolombei (Fig. 79B), there is a distinct slender peduncle, somewhat distended at the tip, at the anterior end. The egg of B. compsilurae (Fig. 79A) is distinguished by the possession of a membranous envelope which conforms to the shape of the egg body but is considerably larger, and the anterior end bears a roughened micropylar area similar to that of the egg proper (Dowden, 1935).
Egg incubation is completed in 2-3 days in all species. In endoparasitic species there is no notable increase in size during this time.
Superparasitization seems frequent in occurrence in most species, because the females demonstrate no discrimination in the choice of hosts for oviposition. Usually the surplus individuals are destroyed by combat during the first larval stage, although Roberts indicated that they may attain the second stage in B. fonscolombei. Two larvae of Euchalcidia can develop to maturity on a single host if the eggs are placed upon opposite sites of the body. In competition, the older larvae are usually able to overcome younger individuals.
The first instar larvae are of two types, the hymenopteriform and the caudate. The first named is found in the ectoparasitic species and in those which are endoparasitic in lepidopterous pupae, and the caudate larva occurs among the species that develop in dipterous pupae. The hymenopteriform larva of B. intermedia, which is characteristic of that type, is somewhat elongate, with a large, lightly sclerotized head and 13 distinct body segments of approximately equal length, each of which, except the last, bears three pairs of sensory setae and numerous cuticular spines, particularly on the venter. There are four pairs of spiracles, situated on the second thoracic and the first three abdominal segments. B. femorala and E. caryobori are said to have only two pairs of sensory setae on each segment.
The caudate first instar larva, represented by B. compsilurae and B. fonscolombei (Fig. 79C, D) has 11-12 distinct body segments followed by a tail representing one fifth to one third of the total length. In B. fonscolombei, the tail apparently represents the fused twelfth and thirteenth segments. There appear to be no sensory setae; but each segment bears a partial or complete ring of cuticular spines, and these occur also upon the tail, though irregularly distributed. An internal tracheal system is present, but there are no spiracles.
Larval feeding period is short, being completed in one week or less except in B. compsilurae, which has an active larval period of variable length, because development does not progress beyond the first instar until the host pupates. Very soon after pupation the feeding of the parasitoid larva results in the formation of a bubble-like area in the host body; and, after the first molt, it can usually be found in this space (Clausen 1940/1962). In B. compsilurae and other species attacking dipterous hosts, the contents of the puparium are completely consumed, and the size of the adults is consequently variable and directly dependent on that of the host individuals. In contrast, species that develop in lepidopterous pupae only partially consume the pupa which contains sufficient food for several parasitoids. Only one parasitoid individual ever develops to maturity, however. When feeding is completed the unconsumed portion is partitioned off from the cell in which pupation will take place. This semifluid surplus is usually in the abdomen, for parasitoid feeding is limited to the anterior portion of the pupa, and in smaller host individuals it dries out quickly so that protection for the pupa is unnecessary.
The second instar larva is more robust, and, in the caudate form, the tail persists, though reduced in size. There appears to be no uniformity in spiracle number or arrangement. B. compsilurae still has none; B. intermedia retains the four pairs present in the first instar, of which those on the mesothorax are much the largest; and B. fonscolombei (Fig. 79E), B. femorata, and E. caryobori have nine pairs, situated on the second and third thoracic and the first seven abdominal segments.
The third instar larvae show a further convergence of the two forms. In B. compilurae, the sensory setae first appear at this time. All species have the nine pairs of spiracles arranged as given above. The fourth instar larva presents no distinctive features.
The fifth instar larvae of Brachymeria and Euchalcidia are oval in outline, distinctly segmented, and yellowish white in color. They bear no cuticular spines, but the sensory setae are present though minute. B. fonscolombei (Fig. 79F) and B. compsilurae parasitic in dipterous puparia and having caudate first instar larvae, are further distinguished from others of the family by the possession, in the mature larva, of yellowish, wedge shaped sclerotized plates situated just below the spiracles of the second to seventh abdominal segments. The function of these is unknown. The spiracles are as in the preceding two instars.
It was noted by Roberts that B. fonscolombei emerges in the spring only from puparia that were formed the preceding autumn and that hosts that have passed the winter in the mature larval stage are unparasitized. This indicates an acceleration in development of the parasitized hosts, or rather a stimulus to pupation, comparable to that brought about by the braconid Alysia manducator Panz. in Lucilia and other hosts.Information courtesy of www.faculty.ucr.edu
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