Mate and nestmate recognition in the primitively eusocial wasp Ropalidia marginata

Abstract

Chemical communication has a vital role in social insects. Chemicals like cuticular hydrocarbons (CHCs) are involved in eliciting behaviors such as nestmate and mate recognition. For CHCs to act as mate recognition chemicals, they should be sexually dimorphic. It is known that there is no sexual dimorphism of non-volatile CHCs. So, we checked if males and females of the primitively eusocial wasp, Ropalidia marginata, vary with respect to volatile CHCs (if any). Our results, from gas chromatography suggest no volatile CHCs and confirm no sexual dimorphism with respect to CHCs, and a bioassay fails to find any evidence for long distance mate attraction, raising more questions about mate recognition in this species. Furthermore, we investigated nestmate recognition in the context of nest when an anesthetized wasp is introduced onto a natal and a non-natal nest. It is known that less than six to eight days old non-nestmate wasps are accepted into nests while older non-nestmate wasps are not. In addition, they both differ in their CHC profile which could be environmentally determined; exposure to nestmates/nest is known to change CHC composition. So, we asked if 13-18 day old wasps, isolated from their nest on their eclosion day, are treated differently than similar age wasps that were allowed to stay on their nest (exposed wasps). Using this, we speculate implications of isolation (after eclosion) on CHC dynamics. Our results show that isolated and exposed wasps are not treated differently, and non-nestmates in both the cases are less tolerated than nestmates. This could mean that when isolated for around 15 days, the wasps have a CHC profile that could be closer to their natal nest profile even after the long isolation from their nest and nestmates, and thus similar (since they may acquire colony labels before isolation from nest) to exposed wasps. However, if a wasp is exposed to a foreign nest and its wasps, its own profile could be overridden by the common colony odor. Our study, done in natural context (of nest), confirms earlier study done in artificial conditions.