Intraspecific competition in antlion larvae: Effects on substrate choice, movement and trap size

Abstract Increasing population density may be particularly important for the selection of hunting sites by sit‐and‐wait predators, such as pit‐building antlions. The objective of our study was to experimentally investigate the effects of intraspecific competition on substrate choice, movement and trap size in the antlion Myrmeleon timidus Gerstaecker, 1888 (Neuroptera: Myrmeleontidae). Third instar antlion larvae were placed in plastic containers (25 × 15 cm, 10 cm deep) with two substrates (5 cm in depth) differing in particle size (fine and coarse). Ten containers received 5 individuals each (high‐density treatment; T5), while another 10 received 2 individuals each (low‐density treatment; T2). Antlion larvae were carefully placed in the centre line of the containers, at the point where the two types of substrates meet. The frequency of traps in the coarse substrate was low (8% in T5 and 15% in T2) and did not differ significantly between competition treatments. Larval movement (i.e., distance from each trap to the centre line) was significantly greater in T5 compared with T2. Neither trap diameter nor depth differed significantly between treatments, but the frequency of small traps was significantly greater in T5 compared with T2. Our findings indicate that M. timidus exhibits a marked preference for fine‐grained substrates for pit construction, regardless of competition intensity. Conversely, our results suggest that an increase in biotic interactions (i.e., exploitation and interference competition) at higher population densities likely compels antlions to move farther to establish their traps and a higher percentage of larvae built smaller traps. We conclude that increasing population density is important for the foraging of semi‐sedentary organisms, as it intensifies competition for space and resources, ultimately influencing growth, survival and reproductive success.