Numbers
Over 750 species in North America in 49 genera.
Identification
First segment of hind tarsi about as long as following two or three combined; most species humpbacked; abdomen with two segments visible dorsally, the remainder telescoped beneath.
Remarks
Three subfamilies: Eucoilinae and Charipinae are parasitic and Cynipinae (about 640 species) are gall makers or gall inquilines, according to Borror and DeLong
(1).
Two subfamilies: Synerginae and Cynipinae, according to Arnett
(2)
Cynipinae is by far the larger subfamily; some of its species can be abundant. Small to minute, usually black, with characteristic shape: the abdomen is oval and somewhat compressed and shiny, the second tergum covers a good part of the abdomen. Each species makes a characteristic gall on a specific part of the plant. Many make galls on oaks. Most have a complex life cycle with a parthenogenetic generation and a sexual one. Each generation makes galls of a different appearance and on different parts of the plant.
(1) P.665
