The regulation of complex building behaviour in the paper wasp, Polistes fuscatus (Insecta, Hymenoptera, Vespidae)

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The paper wasp, Polistes fuscatus, builds its nest by both linear and non-linear construction. Linear construction follows a set sequence of building acts, while non-linear construction can be performed with any of several building acts at a given time. We report on the building programme regulating the non-linear phase of construction and discuss its relevance to the construction behaviour of other species. New cell placement is influenced by distance to the substrate, the location of nearest-neighbour cells (older cells on which the new cell is initiated), the groove between nearest-neighbour cells, orientation of comb and gravity. Gravity also influences many aspects of cell shape, and more cells tend to be added to the lower side of a tilted comb. Amputating one-half of one antenna from wasps demonstrated that the antennae are used for many of the measurements required during construction. Cell lengthening is initially done at a constant rate. Once the larvae become third instars, however, cell lengthening is regulated by larval growth. Wasps use two methods to repair holes in a cell wall: (1) patching and (2) tearing down the wall and rebuilding it. The time to repair decreases with subsequent holes, and some wasps clearly show an improvement in repair technique with experience, suggesting that some learning is involved. The cues triggering the addition of pulp to the petiole, the substrate and the pupal caps and secondary petiole construction were also investigated. These activities are infrequently performed and only specific cues could induce some of them. The decision process involved in non-linear construction can be represented by a non-overlapping branching hierarchy of choice levels. At each construction choice level, multiple cues are evaluated either simultaneously or in a hierarchical manner. Evidently, the more complex nest construction becomes (non-linear construction, multiple building materials, etc.), the more sophisticated the building programme must be. Hierarchical levels of evaluation, sub-routines within the building programme, and learning capabilities appear to be ways of achieving this sophistication.