To house or to oust: How honey bee workers evaluate male quality

Reproductive division of labor is a key feature of the evolution of eusociality. It results in a workforce of generally non-reproductive individuals that undertake the majority of the labor involved in colony growth, defense, and maintenance. The fitness of these workers is derived indirectly through the reproductive caste. In honey bees, Apis mellifera, the reproductives are known as queens (female) and drones (male). As in other eusocial species, workers are able to assess the reproductive quality of their queen. If she is infected by a pathogen or her reproductive output falters, she is replaced. Much less is known about how workers assess male reproductives. Mating occurs outside the hive, yet incoming drones are accepted into a colony despite their significant drain on resources. How do workers decide which drones to accept and care for and which to evict? Here, I determined how and whether workers gauge the quality of drones introduced into their colony. I reared drones of different age categories and induced an immune response using lipopolysaccharide injection to produce drones of varying quality. Each treatment group was sampled for semen analysis, cuticular hydrocarbon profiling, and acceptance into test colonies. Marked drones were introduced to test colonies where both initial acceptance and retention after 24 hours was recorded. My experiment provides foundational new insights into how non-reproductive members of eusocial colonies are able to assess male reproductive quality and use that information to optimize their own indirect fitness.