Wasp who would be queen: a comparative study of two primitively eusocial species

Abstract

Ropalidia marginata and Ropalidia cyathiformis are two Old World, primitively eusocial, tropical polistine wasps that exhibit perennial, aseasonal, indeterminate nesting cycles. Queens are periodically ousted and replaced by one of the workers, whom we refer to as the potential queen. Here we identify the characters of the potential queens by experimentally removing queens from several colonies of both species. Potential queens in R. marginata are unspecialized, worker-like individuals, not unique in their dominance ranks. In contrast, potential queens in R. cyathiformis are queenlike individuals and unique in always holding the top dominance rank among the workers. We suggest that this striking difference in the behaviour of the potential queens of the two species has to do with the very different mechanisms that queens of the two species use to suppress worker reproduction. In regard to their ovarian development, potential queens of neither species are unique and they are only one among several individuals with partially developed ovaries. This may have to do with the fact that queen replacements are frequent in tropical, aseasonal climates, making it adaptive for several individuals to be prepared to take over the position of the queen at short notice.