Heat production by balling in the Japanese honeybee,Apis cerana japonica as a defensive behavior against the hornet,Vespa simillima xanthoptera (Hymenoptera: Vespidae)

As an effective counterattack strategy against predacious hornets, especiallyVespa simillima xanthoptera, workers ofApis cerana japonica showed a distinct balling reaction, usually involving 180–300 bees. This produced heat for as long as 20 min, giving rise to temperatures inside the ball higher than 46°C, which is lethal to the hornet but not to the bees.