Substrate selection in larval Calopteryx splendens (Harris) (Zygoptera: Calopterygidae)

Under experimental conditions, the relationship between substrate composition, with and without the presence of an emergence support, and larval distribution was investigated. Results revealed that C. splendens larvae showed a clear preference for a pebble substrate as opposed to sand or silt, when all 3 substrates were equally available. However, the substrate type decreased in importance as the density of the emergence support increased. Results suggest that the morphological adaptations of C. splendens larvae, to cling to a substrate, can be utilised equally in a vegetated habitat and a habitat predominated by pebbles and cobbles. This has implications for the dispersal of C. splendens to areas containing, traditionally, less favoured habitat. Range expansion of C. splendens on its northern borders, where aquatic habitat characteristics can differ markedly from waterways in lowland southern England, is discussed.