Dominance hierarchies and aggressive behavior among queens of the inquiline ant Vollenhovia nipponica

Abstract

Social parasitism, including temporary paratisism, slave-making, and inquilinism, is one of the most intriguing phenomena in ant societies. Inquiline ants are workerless, completely rely on the worker force of their host ants, and have evolved numerous traits to exploit the host’s resources and to increase their own fitness. We examined the inquiline ant Vollenhovia nipponica, which is a social parasite of the congeneric species Vollenhovia emeryi. Host nests collected in the field usually contained multiple V. nipponica queens, suggesting that it is polygynous. However, the average number of queens in a nest decreased from spring to summer, and many old queens were found dead after the eclosion of new sexuals in late summer. Vollenhovia nipponica therefore appears to have a short life span as found in other inquiline ants. Laboratory observation revealed that inseminated queens were aggressive towards each other. Queen-queen antagonism led to the formation of dominance hierarchies, in which only a few dominant queens developed their ovaries and laid eggs. Subordinate queens frequently left the nests by themselves. The system is very similar to “functional monogyny”.