Size matters: larger galls produced by Eutreta xanthochaeta (Diptera: Tephritidae) on Lippia myriocephala (Verbenaceae) predict lower rates of parasitic wasps

Gall induction is one of the main life strategies of endophagous insects, which serves to provide food and protection against natural enemies. It is proposed that gall size is one of the most important traits in the life history of the inducer insect, since a balance exists between the protection afforded by the gall and exposure to natural enemies. The aims of this study were first to describe the trophic interactions between E. xanthochaeta and its native parasitoids on a new host plant Lippia myriocephala, and then to assess the relationships between gall size, location on the plant architecture and parasitism rates. A community of seven native parasitoid morphospecies was found, representing 22.2% of the overall parasitism, highlighting two wasp species, Torymus sp. (Torymidae) and Pteromalinae (Pteromalidae) as the most abundant. Gall size exhibited significant variations related to their distribution within the plant architecture, with a gradual reduction in size found from the main stem toward the peripheral branches. Such differences were associated with an increase in parasitized pupae and smaller galls were found to be more susceptible to parasitoid attack. Parasitism rates revealed that Torymus sp. uses a broader gall size range than Pteromalinae, and we hypothesized that such variations may be related to certain morphological traits of the parasitoids such as ovipositor length, since the former presents an ovipositor nearly four times longer than the latter. Thus, we infer that growth of bigger galls reduced the likelihood of parasitism of the flies.