In many earlier works, this group has been treated as a subfamily within the family Eupelmidae. However, a recent revision of the group at the species level (LaSalle 1987) has reinstituted the use of the family level and we follow this system. The North American genera were keyed by LaSalle (in Gibson, et al. 1997).

STATISTICS: This is a small group of about 90 species in 9 genera (14 Nearctic species/2 genera).

BIOLOGY: Most tanaostigmatids are believed to be gall-formers on various woody trees and shrubs, especially shrubby legumes (Acacia, Mimosa, Pithecellobium, Prosopis). These may be stem, leaf, or seed galls. A few species have been reported as seed dwellers without gall formation or as inqulines in cecidomyiid galls. Cynipencyrtus flavus Ishii (an old world species) attacks gall forming cynipids and is the only known parasitic tanaostigmatid (its placement as a tanaostigmatid is open to question, see Gibson 1989).

DISTINGUISHING CHARACTERS: In tanaostigmatids the mesopleuron is swollen and convex (as in the eupelmids and encyrtids) and the prepectus is large and swollen anteriorly so that it is visible in dorsal view as well as laterally (this is unique to this family). In addition, the midtibial spur is large and the notauli are present, sinuate, and meet posteriorly at or near the posterior margin of the mesoscutum. In eupelmids and encyrtids the notauli are absent or parallel if present, or not meeting medially (at least in Nearctic forms) and the prepectus is flat.

COLLECTING: In the U.S. tanaostigmatids are found only in the southwestern deserts and southern Florida. In these situations they can be collected by sweeping shrubs (particularly woody legumes in flower) or by collecting the galls from the plants and rearing out the adults. They are not generally abundant.

DISTRIBUTION: This family is primarily found in the tropical and subtropical areas of North and South America, Australia, Asia, and Africa.