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Main diagnostic features
1. Fore and hind tarsi 5-segmented (100%)
2. Small to very large chalcids, body slender to quite robust, from 1-48mm in length (100%)
3. Body usually metallic, often strongly so (70%)
4. Antennae 8-13 segmented (including up to 3 annelli) (100%)
5. Fully winged forms with fore wing with marginal vein at least several times longer than broad (98%), with postmarginal and stigmal vein well-developed, rarely quite short (5%); speculum distinct (99%).
The family currently includes 588 genera and 3506 species placed in 31 subfamilies as follows: Asaphinae (5/25), Austrosystasinae (1/1), Austroterobiinae (1/2), Ceinae (3/15), Cerocephalinae (13/41), Chromeurytominae (3/16), Cleonyminae (42/264), Coelocybinae (15/38), Colotrechninae (19/41), Cratominae (1/3), Diparinae (31/117), Ditropinotellinae (1/3), Elatoidinae (1/4), Erotolepsiinae (4/.4), Eunotinae (23/84), Eutrichosomatinae (4/5), Herbertiinae (1/7), Keiraninae (1/1), Leptofoeninae (2/7), Louriciinae (1/3), Macromesinae (1/12), Miscogasterinae (34/303), Neodiparinae (1/3), Nefoeninae (1/1), Ormocerinae (40/176), Panstenoninae (2/13), Parasaphodinae (1/4), Pireninae (16/179), Pteromalinae (314/2073), Spalangiinae (2/52), Storeyinae (1/2), unplaced (4/7).
The life-histories of taxa in this family are extremely varied, and the group as a whole embraces many of the lifeways exhibited by insect parasitoids. There are solitary and gregarious species, ectoparasitoids and endoparasitoids, koinobionts and idiobionts, primary and secondary parasitoids and even predators.
The majority of pteromalids are idiobionts. Many develop as solitary or gregarious ectoparasitoids of larvae and pupae of Diptera, Coleoptera, Hymenoptera, Lepidoptera and Siphonaptera. Large numbers of species attack hosts concealed in plant tissue, such as wood-borers, stem- and leaf-miners, gall-formers etc. For example, Pteromalus sequester develops ectoparasitically on the larvae or pupae of weevils in broom pods (Parnell, 1964a). The pteromalids associated with galls develop as inquilines, feeding on the gall tissue, or as parasitoids feeding externally on larvae, pupae or even adults of the gall-former (Askew, 1961a). Other pteromalids are strictly ectoparasitoids but develop within a host puparium; for example, Cyrtogaster vulgaris is a fairly common ectoparasitoid of the pupa, within the puparium, of various species of Agromyzidae, Opomyzidae and Chloropidae (Askew, 1965), and the ubiquitous Nasonia vitripennis attacks synanthropic muscids and calliphorids in a similar way. Numerous other pteromalids are idiobiont endoparasitoids. Probably the best known of these, and most reviled by lepidopterists, is Pteromalus puparum a common endoparasitoid of various butterfly pupae, especially those of Papilionidae, Pieridae and Nymphalidae.
Some pteromalids are koinobionts. For example, most species of Miscogasterini are larval-pupal endoparasitoids of agromyzids (Parker & Thompson, 1925; Askew, 1968). Species of Tomicobia are unusual in developing as endoparasitoids of adult Coleoptera (Sachtleben, 1952; Boucek, 1977).
The Pteromalidae contains a number of species that develop as predators rather than parasitoids. The larva of some species of Systasis have been observed to feed on a succession of small cecidomyiid larvae (Ahmad & Mani, 1939; Parnell, 1963). Other species prey on the eggs of various insects. For example, species of Panstenon are known to be predators of the eggs of delphacids concealed in grass sheaths (Rosen, 1956), and eunotines feed on the eggs of Coccoidea; the same pteromalid species sometimes can develop as a hyperparasitoid of the adult female coccid if eggs are not available (Smith & Compere, 1931). A few pteromalids are obligate hyperparasitoids, attacking aphelinids and aphidiine braconids parasitizing aphids.
The fecundity varies from species to species but a female pteromalid may lay up to 700 eggs, placed on or inside the host. The egg may be elongate with rounded ends (Varley, 1937); arched and broadened anteriorly, tapered posteriorly and with a narrow anterior nipple (Cameron, 1939; Askew, 1961b); clothed in minute spicules (Noble, 1932); or bearing hairs and having a pitted appearance (Hussey, 1955). The first instar larva is more or less hymenopteriform with a 13-segmented body, though in some ectophagous or predatory species the larva is somewhat more slender in appearance (see Parnell, 1964b). The last segment may be bilobed and the head is often very enlarged; occasionally the mandibles are also large. Some species may have strong spines on each segment. The first instar larvae of ectophagous species have an open tracheal system, whilst that of endophagous species is closed or completely lacking (Varley, 1937; Cameron, 1939; Hussey, 1955; Askew, 1961b). Pupation may take place inside the dead host, externally in the vicinity of the host, or sometimes inside a host cocoon (Parnell, 1964a). Overwintering is usually as mature larvae, but some species overwinter as pupae or as adults. For example, the females of Cyrtogaster vulgaris overwinter in the foliage of conifers, in leaf litter in tree boles, in tussocks, haystacks, birds' nests etc. (Askew, 1965) and Pteromalus sequester overwinters on its host's food plant (Parnell, 1964a).
As the family is probably polyphyletic a brief synopsis of the biologies is presented here by subfamily (occurrence of subfamily in Europe indicated by [*])
Species of Asaphes are hyperparasitoids of aphids via aphidiine braconids and aphelinid chalcids (Haviland, 1922; Dunn, 1949; Evenhuis, 1964). A North American species of Hyperimerus is recorded as a parasitoid of chrysopid and hemerobiid Neuroptera (Burks, 1979). Species of Bairamlia are of interest on account of their association with vertebrate ectoparasites. B. fuscipes has been reared from the cocoons of the flea Ceratophyllus wickhami, which is an ectoparasite of the Grey Squirrel (Sciurus carolinensis) (Waterston, 1929). Another species, B. nidicola, is associated with the nests of various birds (Ferrière, 1934), possibly as a parasite of the poultry flea, Ceratophyllus gallinae. Some females of B. nidicola collected from the nest of a sand martin (Riparia riparia) had their wings bitten off at about the level of the junction of the parastigma with the marginal vein. It appears that the female does this to facilitate movement within the nest (Graham, 1969).
Associated with galls on Eleocarpus sp. in Australia and possibly phytophagous.
A very small subfamily which has been recorded as parasitoids of the larvae of leaf-mining Diptera of the families Agromyzidae and Drosophilidae (Boucek, 1961).
Parasitoids of the larvae of beetles and one species, Cerocephala rufa, may develop as a hyperparasitoid of scolytids or anobiids via a doryctine braconid primary parasitoid (Szczepanski, 1960; Burks, 1979). One cosmopolitan species is a very common parasitoid of a variety of anobiids, bruchids, curculionids and ptinids, including species of economic importance (Williams & Floyd, 1971).
In Australia, associated with galls on Eucalyptus and Acacia and reared from leaf mining Lepidoptera (Gracillariidae) (Boucek, 1988)
Cleonymus laticornis has been reared in Britain from a cerambycid, and the other British species, C. obscurus, has been reared in France from a scolytid (Kerrich & Graham, 1957). In Europe, a cleonymine, Pannoniella sexramosa, is known to develop as a parasitoid of a eurytomid that inhabits the culms of grasses (Boucek, 1958). Species of one North American genus, Epistenia, are known to parasitize various stem-nesting aculeates (Krombein, 1959).
Hosts unknown, but associated with galls on various trees in Australia, New Zealand and South America.
In Australia, a species of Cameronella has been reared from the galls of Apiomorpha (Hemiptera: Eriococcidae), species of Amerostenus, Pachyneuronella from galls on eucalypts and Casuarina, a species of Errolia from an anthribid beetle (Boucek, 1988). One species of Colotrechnus has allegedly been reared from an agromyzid. A North American species has been found to emerge from the heads of some Asteraceae.
Hosts unknown, but one species has repeatedly been observed to be associated with wooden posts etc. (Graham, 1969).
The females of Dipara petiolata are generally wingless and the males are fully winged and look very different. Species of this subfamily are possibly parasitoids of beetle larvae, though the host of D. petiolata is not known.
The species develop in galls on various Eucalyptus, Acacia and Casuarina species in Australia and New Guinea including the galls of Apiomorpha frenchi (Hemiptera: Eriococcidae) Froggatt on Eucalyptus rostrata (Boucek, 1988).
Recorded as parasitoids of several species of Phenacoccus (Hemiptera: Pseudococcidae) (Kamijo, 1983).
Hosts not known.
Eunotines are parasitoids or hyperparasitoids of Coccoidea, or develop as predators on coccoid eggs within the body of the female (Smith & Compere, 1928; Flanders, 1953; 1959). Several species have been transported from one country to another as part of biological control programmes (Burks, 1979).
Last updated 07-Jun-2004 Dr B R Pitkin