Discrimination of larval sex and timing of male brood elimination by workers in honeybees (Apis mellifera L.)

Abstract

To test a hypothesis that workers in social Hymenoptera can identify male broods at early stages of development and eliminate them to avert excessive investments in male brood, the ability of larval sex discrimination and the timing of male brood elimination by honeybee (Apis mellifera L.) workers were determined. A comparison between the egg sex ratio and the sex ratio of 5 day-old larvae showed that male larvae might selectively die and/or be eliminated in colonies with low survival rates of broods. Nurse bees conditioned by the extracts of male larval cuticles responded significantly more frequently to male extracts than female ones extracted from 3 and 4–5 day-old larvae. It is known that during the developmental stage of 4–5 days, the weight sharply increases in male larvae. The nurse bees conditioned by the extracts of male comb cells failed to distinguish between male and female extracts. Honeybee workers can thus discriminate the sex of broods for male elimination based on cuticular substances during the larval periods with the highest growth rates, which may avert excessive investments in male brood.