The complexity and hierarchical structure of tasks in insect societies

To understand the functioning and organizational complexity of insect socie ties, a combination of different approaches is needed. One such approach, w hich we adopt in this study, is to consider tasks in insect societies not b ased upon their function, as is traditional, but upon their structure. Four types of task in insect societies have been proposed: individual, group, t eam and partitioned tasks. We examine the relationships among these four ta sk types and consider 'task complexity' to mean the degree of cooperation a nd coordination required to complete a particular task successfully. In thi s respect, individual tasks are considered the simplest (low complexity), g roup tasks are more complex (medium), and team and partitioned tasks the mo st complex (high). We decompose tasks into their component subtasks to unde rstand how the demands of a task influence how workers must work together t o complete it successfully. We describe a simple method to measure the comp lexity of tasks using task deconstruction. Points are assigned to each subt ask within the task and summed to give a total score. This measure, the tas k's score, allows objective comparison of tasks (different tasks may be ran ked in order of their complexity) within and between species, or even highe r taxa, and we hope it will be of practical use to researchers. We propose that both team and partitioned tasks may contain individual, group, team an d partitioned subtasks. We examine each of the possible task-subtask relati onships and provide examples from known social insect behaviour. (C) 2001 T he Association for the Study of Animal Behaviour.