The behaviour of queens and potential queens in the primitively eusocial wasp Ropalidia Cyathiformis
Student name: Ms Nitika Sharma
Guide: Dr Joachim Michael Schmerbeck
Year of completion: 2013
Host Organisation: Centre for Ecological Sciences, Indian Institute of Science, Bangalore
Abstract: For this study, fifty three hours of observation were made in total on two naturally occurring
nests of Ropalidia cyathiformis. These observations were made to find out if dominance
behaviour shown by the individuals can be used as a proxy to identify the queen and potential
queen in this species. Ropalidia cyathiformis lacks any morphological distinction between the
reproductive and non reproductive castes (hence termed primitively eusocial). The queen is
identified solely on the basis of egg laying. However, this species is also found to be polygynous
(having more than one egg layer per colony) and the queen is defined as the major egg layer in
the colony. R. cyathiformis displays a plethora of intriguing behaviours and a diverse repertoire
of dominance behaviours among a select few proportion of individuals in the colony. Due to the
aseasonal and long nesting cycles, the wasp colonies are known to undergo natural queen
turnover frequently. The queen is often overthrown by one of the workers, a Potential Queen,
who eventually takes over as the major egg layer, becoming the new queen in the colony. It was
found in the study that although the potential queen could not be identified very clearly in the
presence of the queen, once she was removed, the potential queen was the most aggressive
individual who was never, in turn dominated upon by anyone. There was an evident amplification
in the frequency of dominance behaviour shown by the potential queen soon after queen removal.
Aggression is assumed to be an honest advertisement to ensure the quality of the potential queen
in the midst of the workers, who would eventually have a stake in the new queen’s reproductive
fitness. In the study, it was found that the PQ identified on the basis of dominance behaviour was
observed to lay eggs in both the nests observed, thus confirming dominance behaviour to be an
effective proxy for queen status in R. cyathiformis. As a study model, Ropalidia cyathiformis
makes up for an indispensable backdrop to view the foundations of the more complex and
sophisticated stages of social evolution in Hymenopterans.
Key words: Eusociality, Potential queen, Dominance behaviour, Inclusive fitness, Evolution.
