Defensive and Offensive Behavioral Interactions between Shelter-Building Caterpillars and Hunting Wasps

Many animals build shelters to avoid predation, but some predators cope with these shelters to prey on them. To explore the behavioral interactions between shelter-building prey and their predators, we investigated the shelter defenses of two caterpillar species (Lepidoptera: Crambidae) and the hunting behavior of each predator species (Hymenoptera: Vespidae: Eumeninae) under laboratory conditions. Female wasps of Anterhynchium flavomarginatum and A. gibbifrons were observed attacking the larvae of Haritalodes derogata and Demobotys pervulgalis (Lepidoptera: Crambidae), which construct open and closed leaf shelters, respectively. The attack behaviors differed between the two wasp species. Anterhynchium flavomarginatum employed two attack strategies: (I) boring holes in shelters and driving caterpillars out, and (II) invading shelters and searching for prey inside. In contrast, A. gibbifrons utilized a single strategy: cutting the silk threads binding the leaves with their mandibles to open the shelters and search for prey inside. Approximately half of the prey caterpillars could avoid predation; the shelter morphology and behavior of each caterpillar species likely contributed to evading the wasps. Each caterpillar species may have adapted a specific anti-wasp defense, while each wasp species may have acquired offensive traits to overcome the defense of each prey.