The family consists of three subfamilies, of which only the Cynipinae do occur in Europe. The Cynipinae in turn consist of four tribes: the primitive Aulacideini, that cause galls on a wide variety of plant genera, the Rhoditini, that cause calls on Rosa, th very large group of the Cynipini, all gall causers on oak, and finally the rather heterogenous group of the Synergini, that live as inquilines of other Cynipidae.
In many Cynipini an alternation of generations does occur, in which a sexual generation of males and females (generally in spring) alternates with an asexual generation of only females (generally later in the season, also overwintering). The galls and the adult insects of the two generations are strongly different; often the two generations also have different host plant. Discovering the relation between both generation has not yet succeeded for all species. However, recent work by Stone ao (2008a) has demonstrated that the number of Andricus species with only an agamous generations is small, or perhaps non-existing.
The development of the gall is steered by the saliva of the wasp larva. This forms an interesting contrast with the situation in sawflies (Tenthredinidae, the “Pontania-complex”), where gall formation is initiated by the oviposition of the female.
The number of parasitoids and inquilines that can be found in cynipid galls is staggering; an first introduction in this multitude is available in the catalogue by Askew ao (2013a).
Askew, Melika, Pujade-Villar ao (2013a), Cook, Rokas, Pagel & Stone (2002a), Cook, Stone & Rowe (1997a), Gauld & Bolton (1988a), Graham, Stone, van der Ham & Brewer (2008a), Hellrigl (2012a), Liljeblad (2002a), Melika, Csóka & Pujade-Villar (2000a), Nieves-Aldrey (2001a), Pujade-Villar, Bellido, Segú & Melika (2001a), Rokas, Melika, Abe ao (2003a), Stone, Atkinson, Rokas ao (2008a), Stone & Cook (1998a), Stone, Schönrogge, Atkinson ao (2002a), Williams (2010a).