Tetrastichinae

Tetrastichinae is a subfamily of the chalcid wasp family Eulophidae. It is one of the largest subfamilies of the Eulophidae containing over 100 genera and nearly 3,000 species. The species of the family Tetrastichinae are found in almost any type of terrestrial habitat and have a worldwide distribution, except Antarctica. They show a varied biology and hosts for Tetrastichinae wasps have been identified from over 100 different insect families, across 10 different orders and they have also been recorded as being parasitoids on nematodes, mites and spiders' eggs. Some species are even phytophagous, while others are inquilines and yet others are gall formers.

==Biology== The Tetrastichinae contains species which are mainly parasitic, although some species are known to be phytophages. Phytophagy has so far been shown to be secondary, especially in species in which the larvae are inquilines with gall forming insects and primary phytophagy has not been demonstrated. Endoparasitism is more frequent than ectoparasitiusm and taxa of either parasitic type may be gregarious or solitary. In the gregarious forms a single host may support very few parasitoids or it may host many of them, for example in a single chrysalis parasitised by Aprostocetus xanthopus over 2000 larvae were found. Sometimes hyperparasitism is shown, with the species in the genus Eutetrastichus (now synonymised with Baryscapus) in particular being hyperparasites, and hyperparasitism may be obligate but it can also occur opportunistically in response to circumstance.