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Eulophidae

NOTE: A recently published reclassification of the Eulophidae based on a phylogentic analysis of the D2 region of 28s rDNA gene has shown that the family Elasmidae should now be regarded only as a tribe within the family Eulophidae (Gauthier, et al. 2000).

Main diagnostic characters

1. All tarsi 4-segmented (100%)
2. Antenna (excluding anelli) 7- to 9-segmented, with at most 4 funicle segments, but in addition there may be up to four anelli present (100%)
3. Gaster with a distinct petiole so that there is a distinct narrowing between the propodeum and gaster (100%)
4. Foretibial spur usually straight and simple (95%)

Included taxa

The family currently includes 297 genera and 4472 species placed in 4 subfamilies as follows: Euderinae (17/148), Eulophinae (97/1316), Entedoninae (87/1307), Tetrastichinae (91/1644), unplaced (5/57).

Hemiptarsenus wailesellae Stenomesius rufescens
Eulophinae
(Hemiptarsenus wailesellae)
Eulophinae
(Stenomesius rufescens)
Perthiola mazaneci
Eulophinae
(Perthiola mazaneci)

Biology

The majority of Eulophidae are primary parasitoids of concealed larvae, especially those inhabiting leaf mines. The best known species attack Lepidoptera, but many species parasitize larvae of other insects living in similar concealed situations (such as Agromyzidae, heterarthrine Tenthredinidae and Curculionidae). Other eulophids attack various gall-forming species of insects, eriophyid mites (see Boucek & Askew, 1968) and also gall-forming nematodes (Berg, et al. 1990). Various other species collectively exhibit a great range of lifeways. The European species Dahlbominus fuscipennis is an ectoparasitoid of prepupae or pupae of diprionid sawflies in cocoons (Morris & Cameron, 1935). Eulophus and Euplectrus species are gregarious ectoparasitoids of exposed, leaf-feeding lepidopterous larvae. When fully-grown these parasitoid larvae often pupate on leaves around their dead host (Gradwell, 1957). A number of other eulophids develop as endoparasitoids in insect eggs. Amongst these Mestocharis bimacularis is unusual in attacking dytiscid beetle eggs when they are exposed by fluctuating water levels (Jackson, 1964). Entedon ergias, which oviposits in the eggs of various beetles, especially those of scolytids, is unusual in being an egg/larval parasitoid (Beaver, 1966). Tetrastichus mandanis also starts its larval life as an endoparasitoid in an egg (of a delphacid), but emerges from the egg during its second instar, and becomes a predator that actively searches out other homopteran eggs (Rothschild, 1966). Another British species of Tetrastichus is recorded as having a completely predacious larva which develops by consuming a number of cecidomyiid larvae in a single pod of Sarothamnus (Parnell, 1963).

Species may be idiobiont ectoparasitoids (Eulophinae, Euderinae), or endoparasitoids (Entedoninae and many Tetrastichinae). Many endoparasitic species are idiobionts (eg most Chrysocharis spp.), but some (eg Chrysocharis phryne and Achrysocharoides spp.) are koinobionts (Askew & Shaw, 1979). Many idiobiont species can behave as facultative hyperparsitoids (Askew, 1968; Askew & Shaw, 1979) and hyperparasitism is usual or even obligatory in some species. Pediobius brachycerus, for example, is an obligatory hyperparasitoid in spider's egg sacs. Solitary species probably outnumber gregarious species in Britain, though both forms of development are common and are often found within single genera. Bridging these rather rigid habits are a number of species that develop in broods of from one to a few, depending on host size. In some species of Achrysocharoides, including the British species A. niveipes and A. latreillei, the male develops as a solitary endoparasitoid, whilst the female is a gregarious endoparasitoid (Viggiani, 1964; Askew & Ruse, 1974; Bryan, 1983).

The egg is normally elongately oval or kidney-shaped (Cameron, 1939; Clancy, 1946; Askew & Ruse, 1974), or occasionally with a long anterior filament (Viggiani, 1971) which probably serves to anchor the egg to the integument of the host (Silvestri, 1911). There are from three to five larval instars. The first instar eulophid larva is hymenopteriform, 13-segmented, and occasionally has fleshy tubercles or rows of spines on its body. The mature larva is generally not hairy (Askew, 1968). The larvae of some species (eg Diglyphus, Chrysocharis) construct a circle of little faecal pillars about themselves (Viggiani, 1964). The larva pupates within this circle and the pillars harden to serve as "pit props", preventing the collapse of the host mine as the plant tissue dries out (vide Askew, 1971: fig. 69). The larvae of Euplectrus bicolor pupate near or beneath the host and are enclosed in flimsy cocoons (Swezey, 1924). Cocoon formation is very unusual in the Chalcidoidea, and E. bicolor is of interest because its silk is secreted by the malpighian tubules, not by labial glands as is the case in most Hymenoptera. Overwintering is normally as a prepupa or pupa. A few species (eg Necremnus spp.) may overwinter as adults (Cameron, 1939; Askew, 1968). In Britain, most eulophids have more than one generation a year. A few species of, for example, Eulophus and Sympiesis, have different seasonal colour forms, and this condition may occur in the pupae as well as the adults (Gradwell, 1958).

The mating behaviour of some eulophids is very complex and has been described in detail for Melittobia species by Assem and co-workers (1975; 1978; 1982). Mating behaviour can be used to separate closely related species (van dem Assem & Maeta, 1980; Dahms, 1984a) and the evolution of different patterns of behaviour may help in understanding taxonomic relationships (in den Bosch & van den Assem, 1986).

An interesting phenomenon has been reported for Melittobia acasta (Balfour-Browne, 1922; van den Assem, 1975). Unmated females remain with their developing (male) progeny. If the developing males are accessible, the female may stroke them with her antennae, and this behaviour is accentuated when they pupate. The unmated female will mate with one of her emerging sons. If the males are inside a dipterous puparium the female will even gnaw her way in to gain access!

Several species of eulophid are important in biocontrol programmes throughout the world. Notable examples are: Chrysocharis laricinellae, a European species partially responsible for the control of Coleophora laricella (Lepidoptera: Coleophoridae), a pest of larch in North America (Peck, 1963); and Dahlbominus fuscipennis, a European species partially responsible for the control of diprionid sawfly pests of pines in North America (Bobb, 1965).

Brief synopsis of eulophid biologies, by subfamily:

Eulophinae
Eulophines are solitary or gregarious, idiobiont ectoparasitoids of the larvae, or sometimes the pupae, of leaf-miners, or similarly concealed hosts such as leaf-folders, case-bearers, gall-makers and stem-borers. Many species are facultative or obligate hyperparasitoids through other chalcids, braconids and ichneumonids. Some species (Eulophus and Euplectrus) are gregarious ectoparasitoids of the exposed leaf-feeding larvae of large Lepidoptera. A few species of Elasmus have been recorded as primary parasitoids of the larvae of Polistes species (Vespidae).

Elasmus sp. - Female Elasmus sp. - Male
Female Male
Elasmus sp. - Female
Female
Eulophinae
(Elasmus spp.)

Entedoninae
Entedonines are principally solitary or gregarious primary or secondary endoparasites of concealed larvae, or less commonly eggs or pupae. Many of the genera seem to have quite well-defined host ranges. For example, most Entedon species attack beetles; Chrysocharis species parasitize lepidopterous, dipterous and hymenopterous leaf miners; Mestocharis species are egg parasitoids; Omphale species attack cecidomyiid larvae; Ceranisus species are endoparasitoids of immature thrips; and Achrysocharoides species parasitize leaf-mining gracillariid lepidopterous larvae. In some genera, eg Pediobius, a few species appear to have become specialized as hyperparasitoids.

Closterocerus trifasciatus Neochrysocharis chlorogaster
Entedoninae
(Closterocerus trifasciatus)
Entedoninae
(Neochrysocharis chlorogaster)
Entedon urticarii Euderomphale callunae
Entedoninae
(Entedon urticarii)
Entedoninae
(Euderomphale callunae)
Pediobius amorocoelus Tetrastichius sp.
Entedoninae
(Pediobius amorocoelus)
Entedoninae
(Tetrastichus sp.)

Tetrastichinae

Tetrastichines are usually primary endoparasitoids of the eggs, larvae or pupae of Diptera, Hymenoptera or Lepidoptera, through a marked association with small gallicolous hosts. Some even attack eriophyid mites or gall-forming nematodes. A number of species develop as ectoparasitoids or as facultative or obligate hyperparasitoids. Others feed as predators on the eggs of various insects. In some species the first instar larva may be an endoparasitoid of the egg of the host, and subsequent instars become predators on other nearby eggs of the same species.

Aprostocetus ceroplastae Tamarixia dryi
Tetrastichinae
(Aprostocetus ceroplastae)
Tetrastichinae
(Tamarixia dryi)
Baryscopus szoecsi
Tetrastichinae
(Baryscapus szoecsi)

Euderinae

Some species are primary ectoparasitoids of concealed larvae of Lepidoptera or Coleoptera. A few are purported to be endoparasitoids of similar concealed larvae or, in the case of one European species, of the eggs of wood-boring beetles (Strojny, 1952).

Allocerastichichus doderi Boucekastichus leileri
Euderinae
(Allocerastichichus doderi)
Euderinae
(Boucekastichus leileri)
Parasecodes simulans
Euderinae
(Parasecodes simulans)
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Last updated 07-Jun-2004 Dr B R Pitkin