Regulation of nest construction behaviour in Polybia occidentalis

Nest construction by the wasp Polybia occidentalis involves the coordination of three groups of specialized workers; Wood-pulp foragers deliver their loads to builders, who use it to construct the nest. Water foragers transfer water to both pulp foragers and builders, who use it to keep the pulp moist during handling. During a round of nest construction or repair, the levels of activity in the three groups are kept in balance, minimizing queuing delays during transfer of these materials. If the operation is perturbed, balance between the groups is restored, indicating that the system self-regulates. The aim of this study was to determine the sources of information used by each of the three task groups to adjust its level of activity to those of the others. Colonies' responses to experimentally-induced increases and decreases in the flow of each material during nest repair were videotaped in the field in Costa Rica. The results showed that only the builders received information about the nest damage directly from the nest. Feedback between builders determines the level of building activity, which in turn sets the size of the entire repair operation. The level of pulp-foraging activity was determined by information about demand for pulp received by pulp foragers from builders. Water foragers similarly adjusted their group's activity rate in response to feedback received from pulp foragers and builders about the demand for water. Such a chained flow of information from one task group to the next, in reverse order of material flow, allows each task group to fine-tune the size of its effort to that of the group it serves, enabling the whole system to respond efficiently to perturbations. (C) 1996 The Association for the Study of Animal Behaviour