Numbers
More than 800 species in the United States.
Identification
Mostly small or minute insects with reduced venation. Most species are black and the abdomen is usually shiny and somewhat compressed. Filiform antennae; the pronotum extends back to the tegulae and the ovipositor issues from the anterior apex of the abdomen.
Remarks
Gall makers, gall inquilines or parasites.
Internet References
Cynipoidea In Catalan, with excellent photos.