The Disappearance of Eggs and Larvae from the Nests of the Mischocyttarus (Monogynoecus) montei Zikán (Hymenoptera: Vespidae), Especially in Autumn and Winter: Can it Mean an Adaptive Cannibalism to Ensure the Survival of Colonies?

Abstract

The aim of this study was to verify the disappearance of eggs and larvae from the nests of the Mischocyttarus (Monogynoecus) montei, especially in autumn and winter, and at the same time, to discuss about the cannibalism as the main reason for survival of the colonies during the unfavorable climatic conditions. Forty one colonies were studied during the seasons of the year, period from March in 1999 to September 2000. A total of 314 disappearances of immature individuals was counted, corresponding to 95 eggs (27,1 %) and 229 larvae (72,9 %). The results of Chi-Square test for Contingency tables showed that the disappearance of eggs and larvae were significantly higher (P < 0,05)  during the autumn and winter (x2egg= 14,53, G.L.egg= 3, Cegg= 0,38, x2larva= 443,15, G.L.larva= 3, Clarva= 0,81). In addition, the Spearman Correlation test revealed a significant negative correlation (P < 0,05) between the disappearance rate of larvae and fall in temperature (r = ­0,62), as well as between the rate and fall in rainfall (r= ­0,71), in autumn and winter. There were no significant correlation between the disappearance of eggs and any climatic factors. From total number of disappearances, small larvae disappeared from the cells at higher frequency (55,9%, n = 128) than medium (18,3%, n = 42) and large (25,8%, n = 49) size larvae. We suggest that these immatures (eggs and larvae) were cannibalized probably due to scarcity of prey and nectar under unfavorable climatic conditions, especially during the cold and dry periods of the year.