<span>Antlion pits are often spatially aggregated even though there are potential negative effects associated with the aggregation (e.g., heightened competition and predation risk). This study investigated the possibility that a strategy leading to aggregation can be an evolutionarily stable strategy (ESS). In particular, the strategy considered was ‘decreasing relocation tendency when there are neighbors’. An individual based model showed that the strategy can be the unique ESS when the spatial distribution of prey is not completely random and antlions can learn it from their past foraging experiences. A laboratory experiment was conducted to examine the effects of the presence of neighbors and foraging success on the relocation behavior of antlion larvae. Antlions reduced their relocation tendency with respect to these factors, consistent with the predicted ESS. The results suggest that pit aggregations are formed because antlions reduce their relocation tendency when neighbors exist, and this strategy is an ESS.</span>
