A character analysis of the species synergus Hartig, section II (Mayr, 1872) (Hymenoptera, Cynipidae)

A survey is given of the characters used for the differentiation of the species of Synergus Hartig, classified with section II of Mayr. Special attention is given to the phenology of the species, for each of which the life-cycle is schematized, with differentiation in spring- and summer-generation. Two forms, provisionally indicated A and B, could not satisfactorily be identified with any of the known species. Sp. В is a common inquiline of oak-apples; biological observations were made on the larvae. Synergus mutabilis Deitmer, 1924, is synonymized with Synergus albipes Hartig, 1841

Fossil oak galls preserve ancient multitrophic interactions

Trace fossils of insect feeding have contributed substantially to our understanding of the evolution of insect–plant interactions. The most complex phenotypes of herbivory are galls, whose diagnostic morphologies often allow the identification of the gall inducer. Although fossil insect-induced galls over 300 Myr old are known, most are two-dimensional impressions lacking adequate morphological detail either for the precise identification of the causer or for detection of the communities of specialist parasitoids and inquilines inhabiting modern plant galls. Here, we describe the first evidence for such multitrophic associations in Pleistocene fossil galls from the Eemian interglacial (130 000–115 000 years ago) of The Netherlands. The exceptionally well-preserved fossils can be attributed to extant species of Andricus gallwasps (Hymenoptera: Cynipidae) galling oaks (Quercus), and provide the first fossil evidence of gall attack by herbivorous inquiline gallwasps. Furthermore, phylogenetic placement of one fossil in a lineage showing obligate host plant alternation implies the presence of a second oak species, Quercus cerris, currently unknown from Eemian fossils in northwestern Europe. This contrasts with the southern European native range of Q. cerris in the current interglacial and suggests that gallwasp invasions following human planting of Q. cerris in northern Europe may represent a return to preglacial distribution limits