Nematode and Strepsipteran Parasitism in Bait-Trapped and Hand-Collected Hornets (Hymenoptera, Vespidae, Vespa)

SIMPLE SUMMARY: Parasites sometimes manipulate host behavior to effectively utilize their hosts. The parasitism of host-manipulating parasites of hornets (Vespa spp.) was examined for baited or hand-collected hosts. There, two groups of endoparasites that sterilize their hosts, a nematode species, Sphaerularia vespae, and two species of parasitic insects, Xenos spp., were recovered during the survey. Although the nematode parasitism was scarcely observed (4 out of 1641 host hornets), the parasitism of Xenos spp. varied among host species between 0 and 17%. Interestingly, the rate of hornets parasitized by Xenos spp. was higher in baited individuals than in hand-collected ones. Because the bait trap attracts feeding (not foraging for colony) individuals, the parasitism manipulates the host to visit a feeding site, and the result is in good accordance with previous observations; i.e., parasitized hosts frequently visit and stay at feeding sites instead of foraging and reproducing. The present study could be the first case to quantify the Vespa host manipulation of Xenos spp. Genetically, both the Xenos spp. had four haplotypes in the mitochondrial cytochrome oxidase subunit I gene, and these were close to Japanese and some other East Asian genotypes. ABSTRACT: The parasitism of two groups of host-manipulating parasites of hornets was examined in Kyoto, Japan. Vespa mandarinia (661 individuals), V. simillima (303), V. analis (457), V. ducalis (158), V. crabro (57), and V. dybowskii (4) were collected either by bait trap or hand collection with an insect net, and examined for their parasites. An endoparasitic nematode, Sphaerularia vespae was isolated from three overwintered gynes of V. mandarinia and a gyne of V. ducalis. While endoparasitic insects, Xenos spp., were recovered from 13 V. mandarinia, 77 V. analis, two V. ducalis, and three V. crabro, and those recovered from V. analis and others were molecularly identified as X. oxyodontes and X. moutoni, respectively. Comparing Xenos parasitism level and capturing methods, the parasitism level was significantly higher in trapped hosts than in hand-collected ones, suggesting that stylopized hosts are more strongly attracted to the food source (bait trap) compared with unparasitized hosts. The genotypes of S. vespae were identical to each other, and near identical to its type population. While each of the two Xenos spp. showed four mitochondrial DNA haplotypes. A phylogenetic comparison suggested that Xenos haplotypes found in the present study are close to those previously reported from Japan and other Asian countries.