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Spatial distribution of the cockroach, Blattella germanica, in a swimming-bath facility

Rivault, Colette
Entomologia experimentalis et applicata 1989 v.53 no.3 pp. 247-255
Blattella germanica, swimming pools, egg masses, spatial distribution, correspondence analysis, foraging, imagos, molting, larvae, traps, biological development, insects, females
A population of Blattella germanica L. was studied in a swimming-bath facility using a sampling method. A set of traps deposited weekly, over a period of 50 weeks, allowed us to follow the variations of the temporal and spatial distributions of the population inside the building. A Factorial Correspondance Analysis, performed on the data, led us to the conclusion that the population was stable in time. The spatial distribution of the insects was contiguous. Inside an aggregate, we were able to define a circular movement from the center towards the periphery and vice versa; this movement can be superimposed up on the biological development on the individuals. After birth in the middle of the aggregate, during development, larvae explore further a field as far as the border of the aggregate; this exploratory phase, related to foraging behavior or search for new shelters when these become limiting factors, could be considered as the spreading phase of the population. Then, with the imminence of the imaginai moult, old larvae tend to gather in high density areas in the middle of the aggregate. Newly molted adults look for a sexual partner. And finally females remain in the shelters during oothecae maturation.