The family Eulophidae is the largest of the 19 families that form the superfamily Chalcidoidea, and it is a common family that is found practically everywhere. Currently almost 5000 species have been described world-wide, but the majority is probably still unknown and undescribed. Eulophids are found throughout the World but very little is known about the group from the tropics and the majority of the unknown species are to be found in tropical areas.
Members of the family Eulophidae are recognized by having four-segmented tarsi on all legs (except genus Trisecodes which has three-segmented tarsi on all legs), and in having a short and straight tibial spur on the fore leg. These two characters separates eulophids from all other families in the superfamily Chalcidoidea.
The species of eulophids are small, ranging from 0.4 to 6 mm, with the average size somewhere between 1 and 2 mm. The colour varies from metallic to black, to brown, to yellow, to almost white. Many groups of eulophids have a weak exoskeleton and unless treated with chemicals or dried in a critical point drier they will shrivel when they are dead and dried.
The Eulophidae is currently divided into four subfamilies: Entedoninae, Entiinae (formerly named Euderinae), Eulophinae (including genus Elasmus), and Tetrastichinae, all of which occur in the Neotropical region. This family comprises several thousands of species in the Neotropical region, but the majority of these species still awaits discovery and description. Except for the Entedoninae very little is known about the Eulophidae in the Neotropics.
The biology is unknown for the majority of the species, but the available information shows that the biological habits of eulophids are very varied. Most species are parasitoids, i.e. in the larval stage they will feed in or on other insects or spiders, the so-called host, which they through their feeding will eventually kill. The host spectrum is very wide and virtually all groups of insects are recorded as hosts for eulophids. Also spiders and acari are attacked by some species. A substantial amount of eulophid species attack insect-larvae concealed in plant tissue, e.g. leaf-miners, gall-formers and leaf-rollers. Another type of host frequently attacked is free-living insect-larvae, e.g. caterpillars of various kinds. A few eulophids are plant-eaters, mostly in plant-galls induced by other organisms, but in some cases in galls induced by the eulophids themselves.
More information on this group can be found in e.g. Hanson & Gauld (1995 & 2006) and on some of these websites.