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|Classification: Eucharitidae (Family) (= Eucharidae (Chalcidoidea)|
|Eucharis adscendens (Fabricius, 1787)|
The Eucharitidae are a small cosmopolitan family of circa 56 valid genera and 334 species as of 1993. They are most abundant in the tropics. Important morphological characters include antennae 10-14 segmented, lack a club and ring segments (annuli), and the flagellum may be pectinate. The head is lentiform (biconvex) and the mandibles are falcate (sickle-shaped). Most species are metallic and have a rudder -shaped gaster. The head is short; thorax humpbacked; pronotum usually not visible from above; scutellum extends backwards over the base of the abdomen; and the abdomen is stalked and attached low on the thorax.
Known species are primary, solitary parasitoids on the larvae and/or pupae of ants (Formicidae). Their development is hypermetamorphic and involves phoresy. Their eggs are laid in large numbers in dormant buds, opening flower buds, in the stem of inflorescences, in incisions in leaves, in seed pods, or at random on leaf surfaces. The primary larva is a planidium which attaches to a foraging worker ant and is carried into the nest. Once inside the brood chamber, the planidium transfers to and parasitizes a larva or pupa. Subsequent larval instars are hymenopteriform. Most re ectoparasitic, but a few are endoparasitic. Swarms of males sometimes are observed hovering over the nests of ants awaiting the emergence of females. As of 1993 they have found no use in biological control.
Gibson (1993) remarked that the body in Eucharitidae is either with or without a metallic hue. The head is often small relative to the mesosoma and/or thin in lateral view and somewhat transverse triangular to oval in anterior view. The antennae have 8-24 flagellar segments, these sometimes being modified as serrate, ramose, etc. The first segment is similar to the others (Eucharitinae) or ring-like (Oraseminae). The mandibles are usually large and thin in lateral view, and widely crossed over when closed (one on top of the other), and sickle-shaped when open. Mandibles are rarely absent or reduced to pegs. The right mandible has 3 teeth and the left mandible has 2 teeth when not reduced. The labrum is often concealed under the clypeus, but if visible then with apical margin produced into digit-like processes, each process with a long, sometimes spatulate seta (setae usually are visible in a radiating row from beneath the apex of the clypeus if the labrum is concealed). The pronotum is vertical, not visible medially in dorsal view. The mesonotum is abruptly convex above the pronotum. The scutellum is often with a posterior projection or projections. The prepectus is fused to the pronotum (Eucharitinae) or there is a separate sclerite posterior to the pronotum (Oraseminae). The axillae are usually narrowly to widely contiguous medially. The tarsi bear 5 tarsomeres. The metasoma has a petiole that is usually at least as long as wide, often much longer, very rarely transverse. Postpetiolar segments are often somewhat compressed, with the first tergum often covering the following terga. The ovipositor sheath is not exserted.
Eucharitidae are widely distributed but are most diverse in the tropics and subtropics. There are circa 70 nominal genera and 380 nominal species described. Concepts of limits and relationships of this family are not satisfactory. Usually, two subfamilies are included in Eucharitidae: Eucharitinae and Oraseminae. On the basis of larval morphology, Heraty & Darling (1984) hypothesized that Eucharitidae is the sister group of Perilampidae and that Chrysolampinae (Pteromalidae) is the sister group of Eucharitidae plus Perilampidae. Darling (1988) also hypothesized Eucharitidae and Perilampidae as sister taxa based on the digitate labrum, which was thought to be derived from a chrysolampine-like labrum. Bou…ek (1988a) recognized 5 subfamilies: Eucharitinae, Oraseminae, Akapalinae, Philomidinae and Echthrodapinae. Members of Akapalinae have a digitate labrum, while members of Philomidinae and Echthrodapinae have a flap-like labrum. Akapalines are also like many eucharitids because they have thin mandibles, widely joined axillae, and a scutellum that extends posteriorly as a wide, bilobed appendage (Gibson 1993). However, akapalines are also similar to perilampids because they have a transverse pronotal collar and the first 2 postpetiolar terga are fused. Members of Philomidinae are superficially like eucharitids because they share a similar pronotum and a highly convex mesonotum, modified flagellar segments, and somewhat sickle-shaped mandibles, though each mandible has one 2 teeth and one mandible is crossed in front of the other when closed. The labrum is also nondigitate and the axillae are vertical and widely separated. Members of Echthrodapinae are least like eucharitids, similar only in having very narrowly contiguous axillae (mandibles reduced and lobe-like). Except for the nonexserted ovipositor sheaths of females, echthrodapines are more like torymids because they have an occipital carina as well as a setose epipygium and peg-like cerci articulated with metasomal tergum 8. Additionally, the metafemur has a subapical ventral lobe, and one species is known to be ectoparasitic on bee pupae, as are some Monodontomerinae (Torymidae). Therefore, Gibson (1993) included ecthrodapines in the subfamily Monodontomerinae of Torymidae. The combination of attributes possessed by members of the other taxa discussed above also indicates convergence in one or more of the attributes that are used to define or to relate Eucharitidae and Perilampidae. Akapalinae and Philomidinae were thus classified as subfamilies in Pteromalidae by Gibson (1993) "until relationships can be resolved by an analysis of character-state homology and distribution."
Adult female Eucharitidae deposit their eggs into plant tissue, such as leaves and buds, away from the host ant nest. Once hatched the mobile planidium type of larva attempts to attach itself by its mandibles to almost any moving object. The planidium is carried into an ant (Formicidae) nest if it happens to attach itself to a foraging worker ant or perhaps to some ant-nest associate. In at least some instances the planidium feeds on an intermediate carrier, such as a Thysanoptera, which extends the planidium's life until it can transfer to a worker ant. Once in the ant nest the planidium transfers to a larva and stops further development until the larva pupates, after which it initiates feeding and subsequent hypermetamorphic development as an ectoparasitoid (Gibson 1993).
Principal references are Heraty (1985) who keyed the genera and revised the species of Eucharitinae for North America, and Heraty (1989) who established the monophyly of Eucharitinae on the basis of skeletomusculature of the mesosoma. Clausen (1940, 1941) gave detailed observations on behavior and life history of Eucharitidae. Heraty & Darling (1984) described and compared the planidial type of larvae of Perilampidae and Eucharitidae.
This is a homogenous group closely related to Perilampidae, in which adults are often of large size and brilliant metallic green or blue, with some species showing conspicuous modifications in the form of the scutellum, represented by a bifurcate process, the prongs of which may extend to the end of the abdomen (Clausen 1940/1962). Host preferences of members of this family are very consistent, and all species of which hosts are known are parasitic on mature larvae or pupae of ants. The genus Orasema seems to be frequently associated with Pheidole and Solenopsis, Eucharis with Formica, Kapala with Odontomachus, and Stilbula with Camponotus. Wheeler (1907) studied the biology of Orasema viridis Ashm. and other species of that genus. Such early investigations led to the conclusion that all species were probably ectoparasitic, but later two species of Orasema were found to develop internally during their early stages.
NEARCTIC (CANADA).-- Yoshimoto (1984) commented that the family Eucharitidae "is usually easily recognized by the following characters: Body with distinctive shape; head narrow, transverse in dorsal view, usually subtriangular in frontal view, relatively small in comparison to thorax. Thorax well-developed, short, and strongly convex to subglobose dorsally; pronotum reduced, not visible from above; frenulum of scutellum well-developed, sometimes developed as teeth or long apical processes extending over gaster. Gaster usually compressed laterally, rudderlike, usually with long petiole, never sessile; gastral tergite 1 large, either concealing all other tergites or at least covering most of gaster. Antennae usually cylindrical or serrate, in males often branched. mandibles sickle-shaped. Prepectus large, sometimes fused with pronotum laterally."
"All members of Eucharitidae for which the hosts are known are parasitic on ants (Formicidae: Hymenoptera). Their biology is discussed by Clausen (1940). The first instar larvae, like those of Perilampinae, are minute free-living planidia. The adult females oviposit into the buds or foliage of various plants or shrubs away from the actual host ants. Upon hatching, the planidia become active and attach themselves to passing ant workers. In this way they are carried back to the nest, where they transfer themselves to the brood larvae and rest until the prepupal or pupal stage of the host is reached. Development of the parasite then continues to the adult stage. A good description of the life cycle and larval stage of Pseudometagea schwarzii (Ashmead) is given by Ayre (1962)."
There were two subfamilies recognized by Yoshimoto (1984), the Oraseminae and Eucharitinae.
There are 6 genera of this Eucharitinae subfamily recognized in North America, of which Pseudochalcura Ashmead and Pseudometagea Ashmead and probably, Stilbula Spinola occur in Canada (Yoshimoto 1984). Burks (1961) revised North American Pseudometagea Ashmead.
Oraseminae is represented by the genus Orasema Cameron, with 16 species in North America. Species of Orasema for the New World was revised by Gahan 91940) who gave a key to species.
PALEARCTIC (EUROPEAN former USSR).-- Trjapitcyn (1978/1987), as translated from the Russian, described this family as "Moderately large chalcids; body length about 5.0 mm. Antennae with 10 to 14 segments, short basal segment, and without rings. Thorax highly convex; scutellum with denticles or process at apex. First abdominal tergite long and overlaps all other tergites. Legs slender. Ovipositor does not protrude. Body with metallic glaze, sometimes with yellow areas, rarely yellow. Parasites of larvae and pupae of ants. Development through hypermetamorphosis, with exposed planidium or 1-instar larvae. In world fauna 26 genera with more than 140 species are known, most from the tropics; Soviet Union, 3 genera with 26 species (7 species in the European part of the USSR)."
AFRICA.-- Prinsloo (1980) noted that "Structurally, as well as biologically, the eucharitids form one of the most interesting families of the Chalcidoidea. All the species are, as far as known, parasitic on ants, and many species, especially those from the tropical zones, are bizarre in form. The Eucharitidae is a small family, and biologically they are one of the least known groups of the Chalcidoidea."
Relationships & Diagnosis.-- "The eucharitids are probably most closely related to the Perilampidae, the only other family of the Chalcidoidea in which the prepectus is fused with the lateral part of the pronotum. From the latter family, and all other groups of the Chalcidoidea, the Eucharitidae is most readily distinguished by the reduced pronotum and the large sickle-shaped mandibles."
"Moderate to large in size, usually about 4 mm in length; body smooth or coarsely sculptured, often brilliant metallic in colour; head, seen from the front, triangular, small in relation to the robust, bulbously vaulted thorax, the mandibles very large, sickle-shaped; antenna in female usually thirteen-segmented without a differentiated club, the male antenna often branched; thorax with pronotum reduced, not visible in dorsal view, fused laterally with prepectus; apex of scutellum often with processes in the form of a fork or spine; fore wing with marginal vein well developed, usually long, the stigmal and postmarginal veins usually indistinct; abdomen often with a long slender petiole, in which case the gaster is small, strongly compressed laterally; tarsi with five segments."
Biology.-- "Nothing is known about the biology of the African eucharitids. However, it is possible that African forms have habits and biologies similar to the described non-African fauna. As parasitoids of ants, the eggs are laid on plants, and the planidium larva attaches itself to worker ants that frequent the plant; the larva is thus carried into the ant nest where it is transferred to the ant larva. Clausen (1940b) gives a detailed and interesting account on the biology of the Eucharitidae."
"The more common genera of this family are easily distinguished by the scutellar processes. Species of Kapala have a fork at the apex of the scutellum in the form of two long spines. In Stilbulaspis the two prongs of the fork are short, projecting directly from the apex of the scutellum, whereas in Stilbula the two arms are attached to the scutellum by means of a common base; and in Schizaspidia the form is produced from underneath the apex of the scutellum. Our fauna also includes four genera of which the relationships are not fully decided, but they are thought to be best placed in the Eucharitidae: in Philomedes and Aperilampus the prepectus is swollen, appearing on each side of the thorax as two large shoulders, whereas in Orasema and Timeoderus the prepectus is not, as in other eucharitids, fused with the lateral part of the pronotum, but clearly divided by a suture."
INDIA & ENVIRONS.-- Narendran (1988) noted that "The family Eucharitidae comprises perhaps the most wonderfully shaped chalcids. Most of the members of this family are brilliantly coloured and strikingly attractive. Some of them show bizarre form of thoracic scutellum. They are moderate sized individuals and generally measure about 4 mm in length. Eucharitids are closely related to perilampids and both have the prepecti fused with the lateral parts of the pronotum. Eucharitids probably descended from the same ancestral stem that produced the present day perilampids."
"Eucharitids have remarkable host relationships. They are parasitic on ants. The eggs are laid on plants and the planidium attaches itself to the worker ants and so are carried into the ant nest where it is transferred to the ant larva."
Classification.-- "The family Eucharitidae was known in the past as Eucharidae. This family at present consists of three subfamilies viz. Oraseminae, Eucharitinae and Philomidinae; all represented in the Indian subcontinent. Of the eight genera occurring in the region, reports of the genus Eucharis are open to question. The genera Epimetagea Girault and Rhipipalius Kirby were reported from the Indo-Australian region by Hedqvist (1978), but without any species. However, I have included these genera in the key since both Dr. Subba Rao and I believe that they might be present in the Indian subcontinent and will be reported from this region eventually."
AUSTRALASIA.-- Bou…ek (1988) noted that "The family name, based on Eucharis Latreille, was proposed first by Walker (1846a: 21), as Eucharidae. Dalla Torre (1898: 359) corrected it to Eucharidinae and Girault (1928 : 451) used Eucharitinae (with -t-), now accepted as correct (Heraty, 1985: 62)."
"Since exclusion of the Perilampidae from the Eucharitidae by Förster (1856) the definition of the Eucharitidae has changed only little, mainly because most included forms possess rather striking features. The family (at times downgraded to subfamily) was divided into two subfamilies by Kirby (1886: 37) when he erected the Eucharissinae which is here considered as part of Eucharitinae. Apart from the 4 subfamilies recognised here there is one extralimital one, the Philomidinae, which is also included in the generic key below."
"The Eucharitidae are regarded as related to the Perilampidae, probably their plesiomorphic sister-group (Bou…ek, 1956b: 87; Graham, 1969: 7; Heraty & Darling, 1984: 309, 326). However, some plesiomorphies seem to suggest a very early origin, whilst the Perilampidae may have developed later from some other ancestral pteromaloids."
"Eucharitidae are fully winged chalcids which include a variety of peculiar forms. it is still uncertain which of their features belong to the plesiomorphic inheritance from the ancestors, and which are synapomorphic specialisations of the group. For instance, in Saccharissa Kirby the antennae are at least 14-segmented and in the extralimital (southern African) Eucharissa Westwood up to 26-segmented. However, all other aspects of these two genera suggest that such multisegmented antenna is a primitive, ancestral feature and, although unique in Chalcidoidea, it seems not to be a duplication of the segments as is sometimes thought. In many genera the flagellum is branched, often with two rows of long branches, apparently a specialisation. The antennal apex has, however, no specialised function unlike perhaps all other groups of Chalcidoidea. The pronotum is mostly (in Eucharitinae and Philomidinae) strongly reduced in median part and often fused with the prepectus; the fusion may be a derived condition. The axillae are enlarged and usually broadly fused in middle (?groundplan, ancestral feature). Another possible synapomorphy is the falcate mandibles: the left with 2 sharp teeth and the right with 3 (but sometimes mandibles reduced (atrophied): Psilogastrellus Ghesquière, Indosema Husain & Agarwal, Orasemorpha Bou…ek, Echthrodape Burks). Further synapomorphies may be the partly obliterated venation, the frequent obliteration of the malar sulcus, possibly the form of the gaster and of the ovipositor (so far little studied), and the planidium first-instar larva. Phylogenetic evaluation of these characters is not easy. For instance the lack of specialisation of the antennal apex (absence of sensilla, probably due to difference in function) is probably reflected by the unusual variation (above 13) of the number of antennal segments, a feature not found anywhere else in Chalcidoidea, but frequent in Ichneumonoidea. However, when other features are taken into account the multisegmented antenna of Saccharissa and Eucharissa, on which Kirby (1886: 37) based the subfamily Eucharissinae, has only generic value."
Biology.-- "The biology of Philomidinae is not known (thy may be parasites of some ground-nesting bees). Species of Echthrodapinae seem to be parasites of twig-nesting bees (see below). The remaining species of Eucharitidae are probably all parasites of ants (Clausen, 1941; host records listed by Wheeler & Wheeler, 1937: 171-172). The eggs are generally laid in great numbers, either on the leaves or in cuts made by the ovipositor in the leaves (some Orasema, e.g., O. assectator Kerrich in tea leaves in Assam, India; Das, 1963), normal buds (e.g. Stilbula; cf. Clausen, 1940b, 1940c) or flower buds (Eucharis adscendens Fabr., Bou…ek, 1954), among young seeds of inflorescences of some Compositae (Stilbula; see Parker, 1937), or in some other parts of herbaceous plants or shrubs and trees. Some Orasema spp. lay eggs near to thysanopterous eggs on leaves and the hatched planidia feed temporarily on immature thrips (Johnson & al., 1986). The eggs and larvae, especially the first-instar planidium larvae are described for several species (e.g. Clausen 1940a, 1940b; Heraty & Darling, 1984). The habits of the adults of some species have been described also (Clausen, 1941). The planidium larvae are very mobile, some can even jump, and attach themselves to the oncoming insects. Some planidia are eventually carried by the suitable kind of ants into their nests and there get onto the full-grown ant larvae. They develop mostly as ectoparasites of the prepupae or pupae, emerging from the ant cocoons (e.g. Wheeler & Wheeler, 1937; Clausen, 1940b, 1941). The adults seem to live only for few days, not taking any food."
"Eucharitidae are rather well represented in the region, especially in Australia (15 genera), but do not reach New Zealand. The American genera and species are being studied by Heraty (e.g. 1985, 1986). The South European species are treated in the now rather obsolete papers of Ruschka (1924), Gussakovsky (1929) and Nikolskaya (1952). The African forms need extensive study. In Asia the Indian genera were keyed by Narendran (1985: 186-187) and the species were later listed by him (1986: 51-55). The Micronesian species were treated by Watanabe (1958) and several Indo-Australian genera were reviewed by Hedqvist (1978b). Some earlier-described species of the region were placed in Psilogaster Blanchard (these now mainly under Austeucharis) and Eucharis Latreille. The latter genus does not reach Australia and the species in question are found under several other genera, except Eucharis democles Walker, 1939, the single type specimen of which, in the BMNH, is a male of a formicine ant (confirmed by B. Bolton)."
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Adult Behavior.--Mating behavior has been observed in detail in Schizaspidia tenuicornis Ashm. (Clausen 1923) and Kapala terminalis Ashm. This takes place immediately after emergence from the ant nest in both species. On bright sunny days, swarms of male Schizaspidia, often with 100 or more individuals, can be observed hovering 1-2 ft. above the entrance of the Camponotus nest after 9:00am. When a female appears, she is quickly mated. This swarming of the males above the entrance to the host nest seems to be a general habit in many species of Eucharidae, and serves one means by which the host may be quickly determined and the immature stages secured. Males of Kapala rest quietly on foliage near the nest entrance, awaiting the emergence of females. Mating ensues as soon as the latter settle on nearby leaves. Several males of Orasema sp. have been observed in the act of mating with female pupae in the ant nest (Wheeler 1928).
Adults of most species do not require food, particular those species which deposit their eggs en masse; for the eggs are all fully developed at the time of female emergence, and oviposition is completed in 1-2 days. Other species that have a more extended oviposition period, probably feed, and K. furcata F. imbibes honeydew secreted by aphids. Wheeler (1928) mentioned that adults of O. viridis fed on regurgitated material from worker ants.
Oviposition.--The manner by which oviposition in eucharids was discovered was an accident. While surveying insects of wild cotton in Arizona, Pierce & Morrill (1914) found two females of Chalcura arizonensis Cwf. with their ovipositors inserted in apparently healthy cotton squares. Females with squares were placed in vials without being disturbed, and the squares later on revealed compact masses of eggs at the points of ovipositor insertion. This was overlooked by subsequent workers studying the family, and it was not until much later that the same oviposition behavior was noted in another species. Once the problem became generally known, the behavior of a large number of species was determined. In every case, egg deposition has been found entirely apart from the ant host, and a range of adaptations in oviposition habits was revealed (Clausen 1940/1962).
Clausen (1940) separates his discussion of eucharid oviposition according to where eggs are placed as follows:
Female S. tenuicornis selects certain nonresinous trees that have loosely packed buds. Preferred in norther Japan are wild mulberry and chestnut. Just after emergence and mating, the female ascends to a suitable tree, inserts her ovipositor through the bud scales into the central cavity, and lays her entire quota of eggs within circa 20 min. A large number of these masses can be found in each bud, and where excessive, the pressure exerted by the last individuals to utilize the bud is sufficient to force a ribbon of eggs out between the scales or through earlier oviposition punctures. Clausen (1923) found one mulberry bush 7 ft. high to contain an average of more than seven masses per bud, or a total of circa 4 million eggs.
Egg masses of a Korean Eucharis sp. are placed in expanding or fully opened flower buds of Cebata orbicula Kunz. These flowering plants have a remarkable attraction for the female Eucharis; a sprig held over the entrance to the host nest attracts all females in the vicinity within 5 min., and they will cling to it tenaciously. Kapala furcata F. oviposits in the expanding flower buds of Mikania micrantha H.B.K. and an undetermined species of Amaranthaceae in Panama. Only a few eggs are placed in each bud, and the female moves frequently from bud to bud. S. manipurensis Clausen places its large egg mass beneath the outer scales of the loose buds of Flamingia latifolia var. grandiflora. S. convergens Wlk. and Chalcura deprivata Wlk. of Ceylon similarly lay in the buds of the jak fruit, Artocarpus integrifolia, and the latter parasitoid also uses flower buds of croton and Cordia myxa (Clausen 1940/1962).
Stilbula cynipiformis Rossi utilizes seed pods of a small composite plant, Picris hieracioides var. spinulosa Gussone (Parker 1937). Eggs are freed a few days later by the opening of the pod, and egg masses are usually found adhering to the seeds, which are provided with plumes for wind dispersion.
Eggs of K. terminalis Ashm. of Cuba are found on the under sides of leaves of Tragia volubilis L. One female in captivity laid circa 10,000 eggs in 6 hrs. Leaves in the field were so heavily covered with eggs that they appeared overgrown with fungus mycelium (Clausen 1940/1962). Ishii (1932b) recorded the same habit in Parapsilogaster montanus Gir.
Several eucharid genera lay 1-6 eggs, depending on the species, in each incision. Fleshy leaves are most suitable, as they often contain a small cavity by drying out when the epidermis is punctured. Schizaspidia sp. of Malaya favors the large leaves of Medinella and Eugenia, but occasionally oviposits in fleshy stems of blossoms. Incisions are spaced circa 1.0 mm. apart and in distinctly serpentine rows (Clausen 1940). The tissue surrounding the puncture dies and becomes black, resulting in a conspicuous marking of the leaf. Parapsilogaster sp. of Ceylon also oviposits in the half grown leaves of jak fruit, although the incisions are not serpentine in form. Orasema smithi How. and Kapala sp. make leaf incisions in Casearia, Tragia; and O. coloradensis oviposits in those of Stylosanthes biflora in Virginia. Ishii (1932b) noted the same habit for K. foveatella Gir. and Losbanos uichancoi Ishii in the Philippines, with incisions of the latter parasitoid were in two short parallel rows.
Females of a species of Psilogaster in Malaya occur commonly on mango and other foliage that is infested with Selenothrips rubrocinctus Giard. The thrips embeds its eggs singly in the leaf tissue, covering them with a mass of excrement. The female Psilogaster deposits eggs which stand vertically and are evenly spaced, in clusters of 50-100 or more, surrounding a freshly laid thrips egg (Clausen 1940). Oviposition cannot be secured in the absence of the thrips eggs, but there is no good explanation for the association.
Ovipostion habits of Eucharidae |
A ; two egg masses of Schizaspidia tenuicornis inside a mulberry bud.
B ; a cluster of eggs of Psilogaster spp. on the leaf surface around an egg
of Selenothrips rubrocintus.
C ; serpentine lines of oviposition punctures of Schizaspidia sp on the
underside of a fleshy leaf. Each incision contains one to five eggs.
There is a high reproductive capacity, ranging from circa 1,000 in Schizaspidia tenuicornis and other species to 10,000-15,000 in K. terminalis and Stibula cynipiformis. Those with higher reproductive capacities usually deposit the entire quota in 1-2 days. Such a high capacity is necessary for survival of the species in view of a high mortality of the early developmental stages (Clausen 1940/1962).
Development of Immature Stages.--The only species definitely known to pass winter in the egg stage was noted by Clausen (1940) to be S. tenuicornis. Egg masses containing fully developed larvae within, remain in the plant buds from the time of oviposition in late August and early September until springtime. Those which are contained in healthy buds fall from the tree with bud scales when they open, and are apparently lost. A portion of buds die and dry out during winter, which causes the scales to spread apart somewhat. Eggs contained in these buds usually hatch during July, and the planidia escape.
Observations by Parker (1937) on Stilbula cynipiformis point to the possibility of overwintering in the same stage. Oviposition occurs during August-September, and none of the egg masses hatched during the period they were being observed. Eggs of species ovipositing in expanding flower and leaf buds or in incisions in leaf tissue or on leaf surfaces have a relatively short incubation period of 7-15 days.
First instar larvae of Eucharidae are all of the planidium type because they undergo protracted free living periods from the time of hatching until they find a host. Eggs of all species are laid in vines, shrubs or trees, often at some distance from an ant nest, and thus the planidia must find their way into the nest. Planidia of S. tenuicornis emerge from the buds and take up a waiting position on nearby leaves and twigs. The foliage of these trees is infested with aphids at this season, and worker ants are present in sizeable numbers feeding on honeydew. Planidia attach themselves to these workers and are thereby carried into the ant nest, where they move over to the larvae.
In several species of Kapala, Schizaspidia and Chalcura, parasitic on Odontomachus, the above method of reaching the nest is not possible, for ants of that genus do not seem to forage in trees. The difficulty is overcome by the development of a jumping habit, where the planidia stand erect on the caudal sucker and, by use of the caudal cerci, project themselves into space. In this way they reach the ground, and from that point the course of events is the same as in Schizaspidia.
A much different procedure is followed by Psilogaster which is associated with thrips. Parasitoid eggs are fully incubated at the time the thrips eggs hatch, and the young thrips, as it emerges, finds itself surrounded by the cluster of erect Psilogaster eggs. While it is moving around among them, many of the eggs may hatch, and the planidia immediately attach themselves to the thrips. One thrips was found to bear 53 planidia, representing several times its own weight (Clausen 1940). The association is not accidental, for the planidia consistently retain their position until the carrier's first molt.
Host Stage Attacked.--When gaining access to the ant nest, the planidia of the ectoparasitic species attach themselves to almost any larval instar and then await its development to the prepupal or pupal stage before extended growth takes place. In S. tenuicornis, the first molt occurs while the host is a prepupa, and it is the young 2nd instar larva that transfers to the pupa and takes up the feeding position in pleural regions beneath one of the wing pads or hind legs. The host pupa is fully formed before its development is arrested by the parasitoid. However, O. viridis kills its Pheidole host in its prepupal stage, while the appendages are in an incipient stage of development. The parasitoid is usually on the venter of the thorax during feeding. Planidia of K. terminalis are usually attached to the throat of Odontomachus larvae, somewhat to one side. Transfer to the pupa is effected prior to the first molt of the parasitoid, and the appendages of the pupa never attain more than half their full length. Known endoparasitic Eucharidae, such as Orasema costaricensis W. 7 W. and O. sixolae W. & W., attack larvae of Pheidole and Solenopsis, respectively (Wheeler & Wheeler 1937). Planidia were found embedded in the host bodies, with the posterior end fixed in the entrance hole in the integument and surrounded by a collar which was similar to and presumably served the same function as that found among the Tachinidae. It was not determined whether 2nd and 3rd instars were endo- or ectoparasitic, although mature larvae were found moving free in the nest (Clausen 1940/1962).
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Climate and the stage of host brood development influence the life cycle of Eucharidae. In tropical areas, where the ants breed continuously, the parasitoids do likewise. However, in temperate regions there seems to be only one generation per year, with adults present for only a few weeks. In norther Japan, S. tenuicornis emerges during late August and early September, while in Korea the adults may be found in late June. This variation in emergence time seems correlated with the host cycles, which are different subspecies in the two areas. Winter is passed in the egg stage, with hatching taking place the following July. The egg stage thus takes circa 11 months and the 1st larval stage a variable period up to 20 days, after which 7 days are required from the first molt to larval maturity and 6 days for the pupal stage (Clausen 1940/1962).
Eucharis sp. which attacks Formica in Korea, emerges during June, and most of the year seems to be passed in the inactive planidium stage on the bodies of immature host larvae. In Virginia, O. coloradensis Wheeler begins to emerge the first week in July, and adults may be found for only three weeks. Wheeler (1928) observed this species in Colorado during August, but he found O. viridis in the field in Texas during May and June and reared several broods in artificial nests during the rest of the season. Clausen (1940) commented that it is quite certain that these broods did not represent successive generations.
Even though the period of adult occurrence in temperate areas is very short, the life of individual females is even shorter. Oviposition usually begins within an hour, and sometimes within a few minutes, after emergence from the ant nest, and in S. tenuicornis it is usually completed the same day and in 20-40 min. Death follows shortly. In the laboratory giving no opportunity for oviposition, the maximum length of life was 5 days. Adult life is prolonged and oviposition may extend to a number of days in Psilogaster and Orasema, which lay their eggs in small numbers in incisions of leaf tissue, etc.
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The eggs of the Eucharitidae are all of the stalked type and, because of the enormous numbers produced by each female, exceedingly minute. The egg body is ellipsoidal in form and greatly arched dorsally and ranges from 0.1 to 0.2 mm. in length in the different species. The slender anterior stalk is one fourth the length of the egg body in Psilogaster montanus as compared to twice its length in Psilogaster sp. and Stilbula cynipiformis. At deposition, the eggs are translucent, but as incubation progresses they assume a deep amber color, with the heads of the larvae appearing almost black.
The first instar larvae are all of the planidium type, distinguished by a large, heavily sclerotized head and heavy, segmental bands that terminate lateroventrally in pleural plates. These bands are separated by transparent membranes, which are not visible until feeding takes place, and in active individuals the successive segments telescope into those preceding. Because of this, it is difficult to determine the exact number of body segments; but from on examination of cast skins, in which the bands are somewhat separated, the normal number appears to be 12, with the 13th segment represented by the unsclerotized caudal sucker.
The greatest morphological differences between species are found in the form and in the spine equipment of the pleural plates. In Chalcura deprivata (Fig. 66), those of the first two segments are rounded, whereas on the following six segments they terminate in long, posteriorly directed spines which are free, except at the base. The posterior margins of the plates are notched, and those of the fourth and fifth abdominal segments bear a second pair of spines. The paired spines of the latter segment are twice the length of those preceding. The sixth to ninth abdominal segments have the segmental bands but no pleural plates, and the caudal cerci are borne dorsolaterally on the eighth segment. Sensory spines and setae are as shown in the figure.
In Schizaspidia manipurensis (Fig. 66), the sensory spines of the pleural plates are much longer than in Chalcura, and Kapala foveatella, described by Ishii, has the distal portion of the plates of the fifth abdominal segment greatly produced and projecting beyond the end of the body. Several species of other genera show a less pronounced modification of the plates of this segment.
The spiracles, if present, are exceedingly small and difficult to distinguish. In S. manipurensis, the single pair is situated at the anterior margin of the prothorax.
The second instar larva was known only in S. tenuicornis, K. terminalis and Stilbula cynipiformis by 1940 (Clausen 1940). That of Schizaspidia tenuicornis (Fig. 67B) is shining white, with only nine distinguishable body segments, and the head is small, not heavily sclerotized, and situated ventrally. There are no sensory setae or integumentary spines. In K. terminalis, the body is bag like, with only faint indications of segmentation, and a single pair of spiracles is situated at the anterior margin of the mesothorax. Parker's (1932) examination of the 2nd exuviae of Stibula cynipiformis revealed a lack of segmentation, several transverse rows of minute setae, and two pairs of spiracles.
When the host reaches the prepupal or pupal stage, parasitoid larval development is very rapid. A single feeding puncture is made, and except in S. tenuicornis, the parasitoid is not able to make ordered movement after the first molt. The larva of S. tenuicornis and most other genera completely suck out the contents of the host body, while O. viridis removes only a portion. Brues (1919) assumed extraintestinal digestion because of the completeness with which the pupa was emptied. The first exuviae of S. tenuicornis remains attached to the last larval skin of the host, whereas in other ectoparasitic species of Eucharidae it remains adhering to the venter of the 2nd parasitoid instar. Mature larvae of these species bear the two exuviae in leaf-like form on the mid-ventral area of the body (Clausen 1940/1962). Pupation occurs within the host cocoon, if one is formed, or naked in the ant nest. On emergence from the host cocoon, the parasitoid adult thrusts one of its sicklelike mandibles through the envelope and quickly cuts away the entire anterior portion. The ants display no antipathy towards any of the parasitoid stages, and they have been observed to lick the larvae and pupae of Orasema and to care for them as they would their own brood (Clausen 1940/1962).
The mature larvae, which are the third instar, are robust in all species, and they differ principally in the distinctness of segmentation, the presence or absence of dorsolateral tubercles, and the integumentary ornamentation. The larva of Schizaspidia tenuicornis shows no segmentation except for constrictions between the three principal parts of the body. This is true of several other species, but in Eucharis sp. the segmentation is distinct. Large dorsolateral tubercles on the first 10 body segments have been noted only in Orasema. All species bear an anal lobe, usually hemispherical is form, which may represent the last segment.
Although sensory setae and integumentary spines are lacking, yet the body is completely or partly covered with minute papillae or tubercles.
There are usually nine pairs of spiracles, situated on the second and third thoracic and the first seven abdominal segments, though in several species there are said to be only eight. The two pairs on the thorax are much the largest.
It has been pointed out by Parker that the larva of Slilbula cynipiformis is devoid of tegumentary muscles, and this appears to be a normal condition in the family. In no species observed is the mature larva capable of ordered movement, and in many there is no visible physical reaction when they are disturbed.
The pupae of the Eucharidae present few distinguishing characters except in those species which have the scutellum produced into a bifurcate process, in which cases the pupal form is correspondingly modified (Fig. 67D). The abdomen of the female is very large and bears intersegmental ridges over the dorsum and sides. Some species of Orasema, Schizaspidia, Kapala and Chalcura bear welts on the lateral portions of these ridges. These welts, or pustules, are most pronounced in 0. coloradensis; the ridges of O. viridis are unmodified. The welts are globular in form and much constricted at the base and occur only on the posterior thoracic and petiolar regions, in 0. costaricensis.Information courtesy of www.faculty.ucr.edu
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