The mechanism is as follows. Bees complete patrols in random locations that often contain no work. They then conduct random searches for work. Hence, during periods of stable task demand, bees diffuse away from regions of high task demand and return after completing patrols. Although there is continuous movement of individuals, there is no net movement in any direction. Now consider what happens when task demand changes. First, bees searching for work in regions with increasing task demand immediately find it. There is thus an initial jump in task allocation in such areas. Second, because there is continual flux of individuals between regions, bees that finish their patrols in zones with increasing stimulus levels simply stay there instead of moving back to their original locations. There is thus net movement in the direction of increasing task demand. After a variable period of time, all of the regions come to a new equilibrium density of bees. Two environmental contexts lead to shifts in task allocation in [middle age bees]. The first was explored experimentally in this article (fig. 2) and is associated with short-term reallocations necessitated by sharp changes in the environment. These include temperature stress, nest damage, and a host of other phenomena (reviewed in Winston 1987; Seeley 1995). The preceding paragraph describes how the algorithm of this study allows bees to solve such problems. The coupled localization/randomization mechanism leads to an almost immediate shift of labor in any context. The second type of environmental change problem is considerably more complex and still beyond our ability to explain. It has to do with how MABs make longterm changes in labor allocation in response to information received from the forager caste. Task allocation is a rich subject, and it is important to consider how this work relates to previous studies (Jeanne 1986; Gordon 1996; Beshers and Fewell 2001; Sumpter 2006; O’Donnell and Bulova 2007). Two other models, foraging for work and the response threshold model (both reviewed in Beshers and Fewell 2001), in particular, are relevant. Foraging for work is noteworthy in that it stimulated discussion on the important topic of spatial variability in task demand. The model was highly abstract, however. Essentially, the model posited that spatial variability in task demand generates stable task-allocation patterns (temporal polyethism). Individuals work in one place until work runs out, at which point they randomly search for work elsewhere. Because the simulated nest of the model had a concentric structure and because individuals began their lives in the center, the model generated a temporal polyethism-like pattern of division of labor, with young individuals working in the center and older individuals working at the periphery. Excerpted from: A Self-Organizing Model for Task Allocation via Frequent Task Quitting and Random Walks in the Honeybee vol. 174, no. 4 the american naturalist october 2009 *********************************************** The BEE-L mailing list is powered by L-Soft's renowned LISTSERV(R) list management software. For more information, go to: http://www.lsoft.com/LISTSERV-powered.html Guidelines for posting to BEE-L can be found at: http://honeybeeworld.com/bee-l/guidelines.htm