Colony Failure in the Social Wasp Vespa affinis (Hymenoptera, Vespidae)

Nesting populations of the wasps Vespa affinis and V. tropica on Ishigaki Island, Japan, were found to vary dramatically, between high densities in the summer of 1989 and extremely low densities in the summer of 1990. The majority of nests were lost during the early stages of nesting and this could be attributed to four main causes (human, weather, loss of queens, intraspecific usurpation). Intraspecific usurpation was found to be the most frequent and destructive cause of nest failure during the cooperative stage. All usurped nests and most nests which were attacked by conspecific queens failed. The reasons for the failure of these nests and for usurping activity are discussed.