Parasitic behavior of <scp> <i>Amobia distorta</i> </scp> (Diptera: Miltogramminae) and defensive behavior of its hosts, <scp> <i>Anterhynchium</i> </scp> spp. (Hymenoptera: Vespidae: Eumeninae)

Abstract Two Anterhynchium species, A. flavomarginatum and A. gibbifrons , are solitary tube‐renting eumenine wasps that occur sympatrically in Japan. The latter may be a non‐native species that potentially affects native ecosystems through interactions with their parasites. In this study, we observed the parasitic behavior of the miltogrammine fly Amobia distorta , a major parasite of these two species and investigated whether its hosts exhibited defensive behaviors. Among the observed insect parasites, Am. distorta showed the highest parasitism rate on both Anterhynchium species. The parasitic behavior of Am. distorta did not significantly differ between the two host species. Both host species showed similar defensive flight behaviors when the parasite fly approached the host's nest. However, there was no difference in the number of brood cells or intercalary cells per nest between parasitized and unparasitized nests in either species. Differences in the number of brood and empty cells per nest were only observed between host species, suggesting that differences in host nest‐building behavior may be involved.