Egg marking pheromones of anarchistic worker honeybees (Apis mellifera)

Abstract

In honeybees, worker policing via egg eating enforces functional worker sterility in colonies with a queen and brood. It is thought that queens mark their eggs with a chemical signal, indicating that their eggs are queen-laid. Worker-laid eggs lack this signal and are, therefore, eaten by policing workers. Anarchistic worker honeybees have been hypothesized to circumvent worker policing by mimicking the queen egg-marking signal. We investigated this phenomenon by relating chemical profiles of workers and their eggs to egg acceptability. We found that the ability of some workers (anarchistic workers in queenright colonies and deviant workers from a queenless colony) to lay more acceptable eggs is due to them producing significant amounts of queen-like esters from their Dufour's gland. These esters appear to be transferred to eggs during laying and increase egg survival. However, these esters cannot be the normal queen egg-marking signal, as they are generally absent from queen-laid eggs and only increase the short-term persistence of worker-laid eggs, because only 7?30% of anarchistic worker-laid eggs persisted to hatching versus 91?92% of queen-laid eggs. All workers can produce some esters, but only workers that greatly increase their ester production lay more acceptable eggs. The production of esters appears to be a flexible response, as anarchistic workers reared in queenless colonies did not increase their ester production, while some deviant workers in queenless colonies did increase their ester production.