| Foraging behavior for pitfall-trap-building antlion larvae consists of placing and maintaining the pitfall trap to capture prey moving through the environment. Antlion larvae of the species Myrmeleon immaculatus select a habitat and move their pits infrequently after the initial placement. If there are advantages to being bigger, or having a shorter life cycle, then relocating the pit from unproductive sites may increase prey capture rates and (ultimately) fitness. This study investigated possible constraints on antlion foraging decisions.;When fed more, M. immaculatus larvae gained more weight and became heavier adults. M. immaculatus may live with developmental time constraints, since larval size was directly related to adult size, while adult size was inversely related to the time to maturity. Furthermore, antlion larvae could find abundant prey patches within a habitat. A simple satisficing model basing pit relocation on hunger, and an experimental test of the model, showed that data from model and experiment matched closely when capture rates depended on pit location.;Antlion pits in a complex natural environment, Sleeping Bear Dunes National Lakeshore, were in vegetation-covered habitat, a usual distribution for M. immaculatus. Antlion movement in the field was infrequent, so antlions did not track food availability, unless the best feeding sites were under cover. In fact, prey were more numerous in the open, leading to a negative relationship between densities of antlions and of their prey. Some prey were predictable from season to season, although not within seasons. Covered habitats offer protection from high temperature and rain, and may benefit antlions via increased foraging time or reduced physiological stress. In a field manipulation of rain protection, antlions tended to occupy and grow best in unshaded but covered habitat. This elevated growth was not due to different movement rates or prey supply, but to increased foraging in the days after rain.;Trap-building and low metabolic rates may have evolved as a response to food limitation and unpredictable prey. Infrequent movement by foraging antlions may primarily be a long-term response to frequent rains. Increased prey activity after rains may be the most predictable characteristic of their food supply. |
