Habitat Selection by Waterstrider Larvae (Heteroptera: Gerridae) in Relation to Food and Imagoes

Publisher Website
Google Scholar
Abstract
Distribution of gerrid larvae over zones of microhabitat grain was studied in the laboratory. Gerris argentatus obeyed the pattern in nature when all the instars were present (density of youngest instars peaked in the fine-grained zone, of imagoes in the open-water space, and of the two oldest larval instars in the middle zone), but the numbers of all instars of G. lacustris peaked in the middle zone. In experiments with 1st instars, 3 Gerris species preferred the open-water zone, but Limnoporus rufoscutellatus peaked in the fine-grained one. Addition of imagoes caused a shift toward more fine-grained space and a less equal distribution over the zones in all but G. lacustris. Without imagoes, young larvae favoured the space with food, irrespective of whether food was placed in- or outside a fenced area preventing imagoes to intrude. Addition of imagoes to the food space outside the fenced area shifted larval distribution to the fenced refugium. We suggest that interference of older instars against the youngest ones leads to habitat and space shifts of the latter. The effect of food and imagoes on young larvae is hierarchical, imagoes playing the primary role in space shifts. Juveniles are not necessarily excluded from the foraging population, as their microhabitat refugia are not, as a rule, poorer in food than more open water. But imagoes press younger larvae to the fine-grained end of the microhabitat spectrum, thus restricting their foraging in a changing food environment.