Cockroach aggregation: discrimination between strain odours in Blattella germanica.

Behavioural experiments on gregariousness in larval German cockroaches, Blattella germanica (L.), confirmed that this species deposits an aggregation pheromone by body contact. Choice tests with groups of larvae indicated that they were preferentially attracted to papers conditioned by the odour of their conspecifics, although they were able to aggregate on clean paper in the absence of cockroach odour. Individual larvae were able to recognize the odour of their own population or strain in the absence of conspecifics. The odour was produced and perceived by larvae at all developmental stages. We report, for the first time, experiments comparing the relative attractiveness of odours of strains from different locations: larval cockroaches were able to discriminate and recognize the odour of members of their own strain. Our results showed that different strains have variations of a specific odour. All experimental strains had similar discriminatory capacities and all preferred the odour of their own strain. When larvae were presented with a choice between odours from two unfamiliar strains, they appeared to avoid these odours. Copyright 1998 The Association for the Study of Animal Behaviour.