Rate of Strepsipteran Parasitization among Overwintered Females of the Hornet<i>Vespa analis</i>(Hymenoptera: Vespidae)

Abstract

This study aims to infer the proportion of queens and workers of the hornet Vespa analis parasitized by the strepsipterous parasite Xenos moutoni in overwintered females from morphological data collected for three years. It is known that both worker and queen hornets parasitized by strepsipterous insects overwinter. The parasitized queens cannot reproduce in the next season and thus the level of parasitism potentially affects the number of colonies to be established in the population. Thus, estimation of the ratio of parasitized queens to the total of parasitized females would be useful for understanding the population dynamics of the hornet. K-means cluster analysis demonstrated that 50 to 85% of individuals were workers in the total of parasitized females during the period. From 8 to 15% of total queens were thought to be sterilized by X. moutoni, a level that would not be expected to have a serious effect on the population dynamics of V. analis. Forced hibernation of workers might be considered to be a result of manipulation of the diapause system of the host by the parasite to increase its reproductive success.