Effectiveness of the aposematic Eumaeus childrenae caterpillars against invertebrate predators under field conditions

Abstract

Eumaeus childrenae (Lepidoptera, Lycaenidae) caterpillars are specialist herbivores that feed on Dioon holmgrenii (Cycadacea). They are a well–documented case of chemical protection by sequestering cycasin and related compounds from their host. In this study we evaluated the effectiveness of aposematic defenses against chemical and visual invertebrate predators in wild populations of E. childrenae reared on D. holmgrenii. The results from field experiments indicated that the estimated survival and the intrinsic rate of increase in cohorts with predator exclusion were twice those in cohorts without predator exclusion. The visually oriented predators observed were Mischocyttarus wasps and assassin bugs, and the chemically oriented predators were Wasmannia, Crematogaster and Ectatomma ants. Other mortality factors observed were egg cannibalism, nuclear polyhedrosis virus and, reported for the first time, larval parasitism by fly larvae and a fungus.