Foraging behaviour and habitat selection in pit-building antlion larvae in constant light or dark conditions

Abstract

Pit-building antlion larvae are small sit-and-wait arthropod predators that dig conical pits in sandy soils. We investigated the effect of exposure to constant light versus constant dark conditions on antlion behaviour. Antlions tended to relocate less often, construct pits more frequently and construct larger pits in constant light. We interpret this as an indication of dichotomous behaviour under light versus dark conditions such that antlion larvae hunt during the day and modify their positions at night. Antlion larvae immediately responded to the complete switch in this illumination treatment and adapted their behaviour to fit the new conditions. Prey capture success did not differ between the constant light and constant dark conditions. When provided with a choice between light and dark conditions, the vast majority of larvae preferred the former. Those that preferred constant dark, however, were on average larger than those that preferred constant light. We thus suggest that since larger antlion larvae possess larger fat reserves, they can afford reductions in foraging activity (possibly to increase safety). An examination of the antlion trade-off between their preference for light and their preference for sand depth (which may affect their ability to evade predators) showed that their response to illumination was much more prominent, irrespective of the sand depth. Finally, combining light with other factors such as temperature and density may further elucidate microhabitat selection in pit-building antlion larvae.