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Main diagnostic characters
1. Prepectus lying in same plane as, and fused, to pronotum (95%)
2. Pronotum small and hidden by the head dorsally (100%)
3. Gaster usually relatively small with a very long petiole (98%)
4. Fore wing with marginal vein moderately long, stigmal and postmarginal veins extremely short (100%)
5. Moderately large, about 2-5.4mm in length (95%)
The family currently includes 55 genera and 423 species placed in 3 subfamilies as follows: Akapalinae (1/2), Eucharitinae (50/352), Oraseminae (4/69).
All species of eucharitids are internal or external parasitoids of the immature stages of ants. The adult female lays large numbers of eggs (up to about 15,000) on vegetation. The first instar larva is of the planidial type and has been described in detail by Boucek (1956) and Heraty & Darling (1984). It is minute, 12-segmented and has well-developed sclerotised segmental bands which may terminate latero-ventrally in a "pleural plate" that may bear a posteriorly directed spine. The 13th segment is represented by a caudal sucker. The larvae of some species are reportedly capable of jumping (Clausen, 1940), but the British species does not appear to be able to do this (Boucek, 1956). It is not clear whether the first instar larva actively searches out worker ants of the host species, or if it lies in wait until they pass nearby. They attach themselves to the ant and are then carried into the nest. Inside the nest they actively search out ant larvae to which they either attach themselves externally or else enter the body. Further development does not usually occur until the host larva has reached the prepupal stage. There are apparently three larval instars and the latter two are very robust and distinctly segmented. Pupation takes place inside the host cocoon or naked inside the ants' nest.
Boucek (1956) made detailed observations of Eucharis adscendens in the Czech Republic. The adults emerge in moderately large numbers in early June from the nests of Formica rufa. The males swarm above the nest awaiting the emergence of females. Mating usually takes place immediately the female appears. The eggs are laid in groups of 8-15, near the ants' nest, in the closed flowers of the umbellifer Falcaria vulgaris. They are white, with a distinct petiole at one end.
It appears that eucharitids have highly specific oviposition sites on particular species of plants (Clausen, 1940; Heraty & Darling, 1984). A number (eg Eucharis adscendens, Kapala furcata) oviposit into expanding flower buds, whilst Stilbula montanum oviposits through bracts onto graminaceous spikelets. Another species of Stilbula is known to oviposit into the seed pods of a species of Asteraceae, whilst several tropical species from a variety of genera oviposit into incisions made in large leaves. Another tropical eucharitid lays large numbers of eggs on the underside of a plant's leaves, but one of the most bizarre associations is practised by a Malaysian species of Psilogaster which apparently only oviposits onto leaves on which a species of thrips has already oviposited. The female eucharitid was observed to encircle the thrips eggs with a row of her own eggs. The young thrips, whilst attempting to escape from this cordon, may be boarded by a number of eucharitid planidia which remain on the thysanopteran until it moults (Clausen, 1940). The remainder of the life history of this eucharitid is not known.
Ferrière & Kerrich, 1958 (British species, with whole insect figure); Peck, Boucek & Hoffer, 1964 (Central European genera); Heraty, 1985 (North American genera), 1994 (Old World genera), 2002 (World genera).
Boucek, Z. 1956a. A contribution to the biology of Eucharis adscendens (F.) (Hymenoptera). Acta Soc. Zool. bohemoslov. 20:97-99.
Clausen, C.P. 1940. Entomophagous Insects :688pp. McGraw Hill, New York; London.
Ferrière, C.; Kerrich, G.J. 1958. Hymenoptera 2. Chalcidoidea. Section (a) Agaontidae, Leucospidae, Chalcididae, Eucharitidae, Perilampidae, Cleonymidae and Thysanidae. Handbooks for the Identification of British Insects 8(2)(a):40pp, 79 figs, 5 Plates.
Heraty, J.M. 1985. A revision of the Nearctic Eucharitinae (Hymenoptera: Chalcidoidea: Eucharitidae). Proceedings of the Entomological Society of Ontario 116:61-103.
Heraty, J.M. 1994a. Classification and evolution of the Oraseminae in the Old World, including revision of two closely related genera of Eucharitinae (Hymenoptera: Eucharitidae). Life Sciences Contributions, Royal Ontario Museum 157:vii+174pp.
Heraty, J. 2002. A revision of the genera of Eucharitidae (Hymenoptera: Chalcidoidea) of the World. Memoirs of the Entomological Institute 68:367pp.
Heraty, J.M.; Darling, D.C. 1984. Comparative morphology of the planidial larvae of Eucharitidae and Perilampidae (Hymenoptera: Chalcidoidea). Systematic Entomology 9(3):309-328.
Peck, O.; Boucek, Z.; Hoffer, A. 1964. Keys to the Chalcidoidea of Czechoslovakia (Insecta: Hymenoptera). Memoirs of the Entomological Society of Canada No 34:170pp, 289 figs.Previous page | Next page
Last updated 07-Jun-2004 Dr B R Pitkin