Pit size and prey catching efficiency as related to antlion (Myrmeleontidae) size.

Abstract

Antlions, the larval form of lacewings, dig conical pits into which prey fall. The antlions wait at the bottom of the pit. When prey falls into the pit and attempts to escape, the antlion throws grains of sand onto the sides of the pit, creating a mini-avalanche that brings down the prey. We hypothesize that antlion size is positively correlated to pit size and prey catching efficiency. We conducted an initial pilot test and our results falsified those hypotheses. These initial results led us to ask how the soil composition (percent of sand, loam, and clay) affects pit volume. We also wondered if we failed to find a significant relationship between antlion size and pit volume in the initial sutdy because the pits were not built at the same time, giving some antlions unfinished and therefore uncharacteristically smaller pits that others. Since we used antlion area as a measure of size in the first study, weight might have been a better measure of size. To investigate the above possibilities, we repeated the experiment, still hypothesizing that lion size is positively related to pit size and prey-catching efficiency; in addition, pit size will be greater in soils with the highest percent composition of sand. Using weight as a measure of size, we predicted that heavier antlions will build larger pits and catch more ants. If pit size is greatest in soils with the greatest percent composition of sand, mean pit volumes in pure sand will be larger than mean pit volumes in varying mixtures of sand and loam.