Spatial distribution of the larvae of Gomphus pulchellus Sélys (Anisoptera: Gomphidae

The distribution of larval Gomphus pulchellus Sélys in a gravel pit pond near Braunschweig (Lower Saxony, Germany) was investigated by sampling different structure types. It could be shown that the larvae live predominantly in detritus habitats. There were only little differences in spatial distribution between the last four instars. In choice chamber experiments the larvae burrowed themselves mostly into detrituscovered substrates as opposed to uncovered substrates. Given the choice between sediments of different particle size, larvae preferred the finer ones, especially fine sand, but they did not clearly differentiate between sediments more similar in particle size. Comparing the field results with experimental data and findings for G. pulchellus made in Southern France, it is suggested that spatial distribution is influenced mainly by the existence of coarse detritus and to a smaller extent by sediment particle size.