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Earwig travel in relation to habitat Lame, Robert John


In current ecological theory, dispersal and spatial heterogeneity loom large among the processes and patterns thought to influence the dynamics of animal populations. In this study I identify the behavioural adaptations for dispersal displayed by a flightless insect, the European earwig, Forficula auricularia L, and examine some of the consequences of adaptive dispersal for its local populations. The life-history of the species is described. It can be divided into a nesting and a free-foraging phase. Differential nesting success and survival of free-foragers were observed in two kinds of habitat, previous techniques for studying earwig ecology and behaviour are reviewed and compared with some methods especially developed for this study. The parental behaviour of auricularia is compared with that of other earwigs. Three kinds of dispersal from the nest are described: (1) passive dispersal from the nest by second-instar nymphs, (2) active dispersal from the nest by first- and second-instar nymphs, and (3) inter-brood dispersal by females. The latter two behaviours are considered to be examples of adaptive dispersal. The free-foraging phase is a period of growth during which nocturnal foraging alternates with diurnal utilization of shelter. Foraging and sheltering behaviour are described. From the results of field experiments, I conclude that added shelter increases survival, but utilization of shelter is limited by competition for food among insects from the same or from adjacent shelters. Diurnal changes in intra-specific agonistic behaviour and a relationship between shelter acceptance and recent feeding history are the behavioural mechanisms involved. The latter behaviour is considered to be a dispersal mechanism. These results are compared with current concepts of adaptive dispersal in insects and adaptation for life in spatially heterogeneous environments.

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