Optimum antlion pit structure.

Abstract

We investigated the optimal size and shape of antlion (Myrmeleon immaculatus) pits. These pits serve as foraging traps to catch ants and other small insects which are eaten by antlion larvae. The larvae lie in the sand beneath the pits, waiting to strike and capture prey which fall into the pit. We studied pit optimality in both dry and moist sand. Two measurements were used as indicators of pit performance: the amount of time the pit was able to detain an ant (ant retention time), and whether or not the antlion beneath a given pit struck at an ant placed in the pit. In comparing the shapes of the pits, we chose pit steepness and depth as parameters. Neither pit angle nor pit depth affected the pit's performance at any level of moisture. However, when moisture was tested independently, it was shown, at high levels, to reduce the strike rate of antlions.