Bees for Development Journal 123 July 2017
Strong on defence
– movers and shakers, shakers and bakers W S Robinson, Casper College, USA In USA in October 1675, the Wampanoag tribal leader known to European settlers as King Philip was waging war against the encroaching Plymouth Colony in Massachusetts, USA. Roger Williams wrote to the governor of the Massachusetts Bay Colony about one aspect of the famed chief’s military strategy: “Philip’s great design is... to draw... your forces... into such places as are full of long grasses, flags, sedge etc and to surround them with fire, smoke and bullets.” The Asian honey bee Apis cerana (which ranges from India to Japan and is the third-smallest of nine recognised honey bee species) uses a similar defensive tactic, known as ‘heat-balling’ against predatory hornets. Entomologist Masato Ono and his colleagues at Tamagawa University in Tokyo first reported the behaviour in 1987 in the journal Experientia. Guard bees at the entrance of their hive, under attack from giant hornets including Vespa mandarinia, retreat to the recesses of their dark cavity. The voracious hornets, six times the bees’ size, are drawn in behind. Stings are useless against these heavily armoured intruders.
WS Robinson teaches a variety of biology classes at Casper College in Casper, Wyoming, USA. His research interests include the migratory habits of giant honey bees, defences of the Asian honey bee Apis cerana against predatory hornets, and mating behaviour of an Ecuadoran parasitic wasp. Instead, the guard bees, and other worker bees that they recruit by releasing chemical alarm pheromones, surround the hornets in a seething ball, up to five hundred bees per hornet. They vibrate their wing muscles to generate heat. Temperatures inside the balls can reach 47°C, hot enough to bake the hornets - but not the bees - to death. Carbon dioxide generated in the process also weakens and smothers the enemy. Apis cerana, like its European counterpart Apis mellifera is a cavity nesting species building multiple, verticallyhanging wax combs within a dark cavity such as a hollow tree. The cavity and its single, narrow, guardable entrance is the hive bees’ primary defence against
Photo © The International Bee Research Association. Reproduced with the permission of the editors of the Journal of Apicultural Research
A group of Vespa velutina hornets is left behind on a mango branch after a swarm of Asian honey bees has departed.
3
