Abstract

1. Intraspecific competition was investigated in the pit-digging larvae of the ant-lion Morter sp., which normally occurs at low density in a food-rich habitat. 2. Morter larvae interact by displays, challenges, and sand tossing. Challenges/displays affected pit spacing while sand tossing affected pit size. Pit ownership determined the outcome of contests regardless of the relative sizes or feeding condition of the contestants. 3. Competition had no effect on the pit size of winners but losers showed a density dependent reduction in pit size. Interference competition caused a density dependent reduction in larval growth rates. 4. Macroleon quinquemaculatus (Hagen) always won contests with Morter, even when smaller. Cannibalism occurred in 60% of these contests. 5. Little intraspecific competition occurs in Morter in the field. Morter is more willing to incur energy costs than Macroleon.