Family APHELINIDAE
Introduction
The Aphelinidae is a medium-sized family of chalcids that are often overlooked by the general collector due to their extremely small size. They are, nevertheless, quite common and can be commonly reared from a large variety of homopteran hosts. Most aphelinids are primary (ecto- or endo-) parasitoids of Homoptera: Sternorrhyncha (esp. Coccoidea, Aleyrodoidea, Aphidoidea). However, others attack eggs of Homoptera or Orthoptera, and still others are obligatory or facultative hyperparasitoids. A number of these are of particular interest because the males and females of the same species may develop in very different ways. In those species for which the biology has been well-studied, the females are always primary endoparasitoids of Homoptera. The males, however, may develop in the following ways: 1. As primary ectoparasitoids on the same host. 2. As hyperparasitoids on their own species. 3. As facultative hyperparasitoids on their own or other species. 4. As obligate hyperparasitoids on other species.
Economic Importance. There are many examples of aphelinids being used successfully in classical biological control, and this family claims more successes than any other group of entomophagous insects. Apart from their use in classical biological control, aphelinids are commonly major components of various agro-ecosystems, and may be of primary importance in the development of successful IPM programmes.
Distribution. Cosmopolitan.
Classification. The subfamilial classification has by no means been solved adequately, and authors have recognised between three and seven subfamilies. We are using the classification accepted by Noyes (2002). The majority of aphelinids belong to the subfamilies Aphelininae (antenna with six or less segments; linea calva present) and Coccophaginae (antenna with 7–9 segments; linea calva absent).
Important genera: Encarsia, Aphytis, Coccophagus, Aphelinus, Eretmocerus, Centrodora, Ablerus.
Identification of Australian genera: There are no keys to Australian genera; however, Hayat (1983) produced a key to world genera.
Diagnosis
Funicle with 4 or less funicular segments. Tarsi with 4–5 segments. Fore tibial spur large, curved, bifid. Gaster broadly joined to the thorax, not petiolate. Notauli complete, straight, deep; widely separated posteriorly (generally by more than the length of the scutellum). Aphelinids are small or very small, about 0.5–1.5 mm long, and metallic coloration is rare.
General References
Hayat, M. 1983. The genera of Aphelinidae (Hymenoptera) of the World. Systematic Entomology 8: 63-102
Noyes, J.S. 2002. Interactive Catalogue of World Chalcidoidea. (2001, second edition). CD-Rom, Taxapad and The Natural History Museum, London, UK