Over 750 species in North America in 49 genera.
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.
In cynipid galls "the larvae are always in closed cavities. The larvae are never hairy as in the case of the chalcids. Larvae of guest cynipids are not to be distinguished from those of the maker." (1)
Succulent spring galls on oak buds, flowers, and leaves produce fully winged, short-lived males and females. The larvae in the more solid, autumnal galls metamorphose in the fall and depending on species the adults, which are all agamic females, may emerge in late fall (as in Disholcaspis
spp.) or stay in the galls over the winter. Often two or more winters pass before the adults finally emerge. (1)
According to the most recent classification (Ronquist 1999
), all extant cynipids belong to the subfamily Cynipinae, and the fossil genus Hodiernocynips
belongs to Hodiernocynipinae.
Three subfamilies: Eucoilinae and Charipinae are parasitic and Cynipinae (about 640 species) are gall makers or gall inquilines, according to Borror and DeLong (2)
. The first two are no longer placed in Cynipidae.
Two subfamilies: Synerginae and Cynipinae, according to Arnett (3)
. See comment here
describing how they are distinguished.
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. (2)
"The amateur should be warned that a single gall casually collected is seldom worth the trouble of trying to rear. It may be the normal reaction of the host to the stimulus of a cynipid or it may be quite abnormal if it has been modified in size and structure by the attack of guests or parasites in its early stages. Only if found in numbers and on several trees is it probably the characteristic work of a cynipid and worth collecting and rearing." (1)
"Call of the Galls"
article by Ron Russo, in BayNature