Al, Irene Lobato-Vila Et, 2022, A catalogue, revision, and regional perspective of Eastern Palaearctic and Oriental oak gall wasps and their inquilines (Hymenoptera: Cynipidae: Cynipini, Synergini, Ceroptresini), Zootaxa 5161 (1), pp. 1-71 : 51-52

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Cynipini lifecycles and gall induction sites

Excluding the three species known to be purely parthenogenetic ( Andricus pseudoflos , A. targionii and Dryocosmus kuriphilus ), alternating generations have been linked for only 23 of the remaining 100 EPO Cynipini species (23%). If we assume that all of these 100 Cynipini species are cyclically parthenogenetic, then at least 77 additional gall and wasp generations remain to be discovered. Of the 77 (77%) species known from a single generation, and again excluding species known to be purely parthenogenetic, 19 (24.7%) are known only from an asexual generation and 58 (75.3%) are known only from a sexual generation. These values are interesting because in the WP Cynipini fauna, most species known only from a single generation are known from their asexual generation ( Nieves-Aldrey 2001; Roskam 2019). This difference may reflect regional differences in the detectability of the relevant galls. In the WP the mature asexual generation galls of many (though not all) Cynipini are relatively large and often patterned and/or coloured ( Stone et al. 2002; Csóka et al. 2005; Roskam 2019), and persist on the plant for long periods, which may aid their detection. This is less true for the EPO Cynipini fauna so known far, though this does include some very detectable asexual generation galls (such as the large ball or spiny galls induced by asexual generations of Trichagalma ).

With this in mind, knowledge of gall structures and locations on the host plant for EPO Cynipini is very incomplete. Currently known species between them induce galls on all major plant organs (Table 1) and (with some exceptions) each generation of a specific species tends to gall a single plant organ (Table 1). In contrast, alternating generations of the same species often gall different organs on the same plant. Leaves are the most frequent gall induction site (Table 1); most Andricus sexual generations induce integral leaf blade galls, while asexual generations of Belizinella and of Cerroneuroterus induce detachable galls on the underside of leaves. All Cerroneuroterus sexual generations develop in catkins, and the asexual forms of Cyclocynips develop inside stems. As far as we know, the genus showing the greatest diversity of gall induction locations in the EPO is Dryocosmus , which contains species that gall all plant organs except the roots.