2 subfamilies, with >480 spp. in 150 genera in our area and >3700 spp. in 460 genera worldwide(1)
Body length: most adults measure 2-3 mm.
It is one of the families with the mesopleuron as a large, convex, cushion-like region on the side of the thorax. You may or may not be able to see that the middle coxae are inserted at or even somewhat anterior to the middle of the mesopleuron whereas in other chalcidoids the middle coxae are inserted near the hind coxa, much more distant from the front coxae. It should also have transverse-triangular axillae on the scutellum. Other features include a very short marginal vein on the forewing. Note also the very long mesotibial spur. --Gary Gibson
Key to Nearctic genera in (2)
, chapter 8.
Many species are sexually dimorphic, mostly in antennal morphology: females tend to have clubbed antenna with short setae (and sometimes with greatly flattened segments), while males typically lack a club and often have long setae(but never with flattened segments). The taxonomy of the family is mostly based on females (which tend to be more distinctive than males) - in some species males are either unknown or extremely rare.
They are found in a variety of terrestrial habitats, but tend to be more diverse in warmer and drier areas. They can be taken from a wide variety of vegetation (including trees) but are most common on woody shrubs and grasses.
Parasitoids of an extremely wide range of insects (one species is a parasitoid of ticks), but scales and mealybugs (Hemiptera) are common hosts for a large number of species. They can attack the egg, larval, or adult stage, as either a primary or secondary parasitoid.(4)
Includes many important biocontrol agents.
In the past, some workers treated Aphelinidae as part of this family (4)
, but they are now universally regarded as separate taxa.
Malaise traps can be a very rich source of specimens.
Although a few species are fairly robust and can be point-mounted without undue efforts, specimens from the great majority of species will shrink or collapse after death, rendering identification extremely problematic. The best way to preserve encyrtids is to initially keep them in 70-75% ethanol, and later either critically-point dry them, or treat them with hexamethyldisilazine (HMDS)(an extremely toxic chemical that requires a fume hood and personal protective equipment).
As members of the Chalcidoidea, their minute size makes recognition of encyrtids quite difficult. Body colors range from drab dark-brown (or black) to orange or yellow to bright metallic green. Other chalcidoids with which they are most easily confused are the Aphelinidae (due to their general body habitus) and Eupelmidae (due to the enlarged mid-tarsal spurs and mesopleura), but encyrtids can be distinguished by their shorter (often punctiform) marginal vein. However, encyrtids are most often confused with members of the family Platygastridae that had formerly been placed under Scelionidae. Both encyrtids and "scelionids" can have a similar body habitus and forewing venation, making their separation quite difficult for the non-expert.