Cynipoidea

The Cynipoidea have gone through an evolutionary development that approximately parallels that of the Chalcidoidea. Both superfamilies have parasitic and phytophagous forms, although the Cynipoidea does not include known genera that have phytophagous as well as parasitic species. In the Chalcidoidea several genera include phytophagous and parasitic species; in the Cynipoidea no such mixtures occur below the family level. It should be borne in mind, however, that the present classification of the Cynipoidea may have given unjustifiable weight to the habits of the forms placed in the various higher categories. In any case, in each superfamily it is debatable whether the phytophagous or parasitic habit is the more primitive. Although all authorities agree that the members of each superfamily came originally from phytophagous ancestors, there is disagreement as to whether the first Hymenoptera recognizable as representing either superfamily were parasitic or phytophagous. If they were parasitic, as many authorities believe, the present-day phytophagous species are secondarily evolved from parasitic ancestors. The close agreement in essential morphological characters among all members of each superfamily excludes the possibility of polyphyletic origin for the parasitic and phytophagous forms.

The Cynipoidea are a moderate-sized hymenopteran superfamily that presently includes five modern families and three extinct families, though others have been recognized in the past. The most familiar members of the group are phytophagous, especially as gall-formers, though the actual majority of included species are parasitoids or hyperparasitoids. They are typically glossy, dark, smooth wasps with somewhat compressed bodies and somewhat reduced wing venation. It is common for various metasomal segments to be fused in various ways (often diagnostic for families or subfamilies), and the petiole is very short, when present.

With the exception of the Cynipidae (the gall wasps), it is a poorly known group as a whole, though there are nearly 3000 known species in total, and a great many species are still undescribed, mostly in the Figitidae. Each of the constituent families differs in biology, though life histories of one of the families (Liopteridae) are still largely unknown. In July 2020 an identification key for the superfamily was published in the journal Insect Systematics and Diversity, enabling identification to the family level.