Queen loss changes behavior and increases longevity in a stingless bee

Abstract

The death of the queen can lead to behavioral changes in workers of eusocial bees that alter their longevity. Here, we investigated the behavior and longevity of workers in colonies of the neotropical stingless bee Scaptotrigona aff. postica in the absence of a mated queen. Eight colonies, four being queenright, and four with their physogastric queens removed (queenless), were used in experiments. Emerging workers were marked with different colors to obtain age cohorts. We observed external foraging activity, age of workers involved in cell construction and foraging, and worker longevity in all colonies for 100 days. Over time, queenless colonies presented a greater reduction in external activity than queenright colonies; older workers were more frequently observed participating in cell construction and foraging compared with queenright colonies, and worker lifespan in queenless colonies was about a third longer than that observed in queenright colonies. Our study demonstrates that orphaned workers of this species substantially alter their behavior, causing an increase in their overall longevity and workers starting to lay haploid eggs, allowing some direct reproduction by workers in the absence of a queen. For eusocial species, the loss of the reproductive individual is a critical period for colony survival. Our study shows, for the first time, how workers in a neotropical stingless bee species adapt their behavior during periods without a queen. We show that the longevity of workers of Scaptotrigona aff. postica from orphaned colonies on average increased by 33% compared with regular colonies. We also show that many foragers from orphaned colonies spend more time inside the nest building brood cells rather than participating in more risky foraging behaviors. Therefore, workers alter their behavior in the absence of an egg-laying queen; these changes cause a substantial increase of longevity of the labor force (i.e., workers), and consequently, a possibility that the nest survives until a new mated queen resumes oviposition. In case a new queen does not appear in the colony, males produced by egg-laying workers (which gain a direct fitness through direct reproduction) may spread the colonial genome, by mating with queens from other colonies.