Monday, December 10, 2007 - 8:17 AM

In-nest task specialization in the bumble bee Bombus impatiens

Jennifer M. Jandt, and Anna Dornhaus, University of Arizona, Ecology & Evolutionary Biology, 1041 E. Lowell St, BioSciences West 310, Tucson, AZ

Group-level organization is often achieved in social insects through a division of labor, where individuals specialize on particular tasks, such as foraging or defense. In previous studies, little attention has been paid to in-nest tasks due to the difficulty of observing worker behavior inside the nest. Here, we examined the degree to which bumble bees exhibit division of labor with regards to in-nest tasks. Individually marked bees from four colonies of Bombus impatiens were spot-checked daily to determine each bee’s location in the nest and the task they were performing. Our results suggest that B. impatiens colonies maintain a subset of workers that frequently perform brood care, and a subset of workers that spend a high proportion of time performing no task at all. Individuals that are more likely to engage in brood care tend to be smaller, use less area inside the nest, and remain closer to the queen than other bees in the colony. Bees that spend a higher proportion of time performing no task, on the other hand, are not tied to a particular area inside the nest, and are commonly found off of the nest substrate. We found no evidence of task specialization with regards to other in-nest tasks, such as brood warming, cell building, ventilating, and guarding. We conclude that, in bumble bees, brood care may be performed by specialists, but that there is little evidence of division of labor regarding other in-nest tasks.

Species 1: Hymenoptera Apidae Bombus impatiens (bumble bee)