Ken-ichi Harano, Department of Agriculture, Tamagawa University, Machida, Tokyo, 194-8610, Japan, Yukinori Shibai, Department of Agriculture, Tamgawa University, Machida, Tokyo, Japan, Yoshiaki Obara, Behavioral Biology, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, 183-8509, Japan, and Masami Sasaki, Honeybee Science Research Center, Tamagawa University, Tokyo, 194-8610, Japan.
European honeybees (Apis mellifera) often produce large number of new queens in reproductive or emergency queen rearing despite monogyny. This leads to lethal fight among sister new queens for the succession of their natal colony. The elimination of sisters is performed through queen cell destruction and/or duels. In the queen cell destruction, they may prefer to kill older sisters prior to younger ones because older queens will emerge sooner and become dangerous rivals who must be eliminated by duels. To examine this hypothesis, we documented how the “pre-emergence (just before emergence)” and young (10 days old) queen cells were destroyed by newly emerged queens in colonies. We found that pre-emergence queen cells were destroyed sooner than younger queen cells in 3 of 4 colonies (Harano and Obara 2004. Insectes Soc. 51:253-258). In the choice-test conducted in the screen cages, queens discriminated between pre-emergence and 10-day-old queen cells, but did not do so between 7- and 10-day-old queen cells. The results suggest that they prefer to destroy pre-emergence queen cells rather than other ones, but do not destroy them in the order of age from oldest to youngest. Furthermore, we tried to reveal how they discriminate pre-emergence queen cells from other ones. In case that the pupae or eclosed adults were removed from queen cells, they preferred to destroy empty pre-emergence queen cells rather than empty young queen cells. When the movement of eclosed adults within the queen cells was experimentally restricted, they were less destroyed. Based on these results, we suggest that both chemical and auditory cues are involved in the selective queen cell destruction (Harano and Obara 2004. Appl. Entomol. Zool. 39: 611-616). We will also report the age-dependent changes of motivation in queen cell destruction, and different behavioral tactics of queens toward pre-emergence and young queen cells.
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