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The effects of ants on the carnivorous caterpillar Feniseca tarquinius and the role of chemical camouflage in the Feniseca-ant interaction.
Youngsteadt, Elsa*,1, 1 University of Wisconsin-Milwaukee, Milwaukee, WI, USA
ABSTRACT- The majority of caterpillars in the butterfly family Lycaenidae are myrmecophilous, that is, they provide ants with nutritional secretions in exchange for protection from natural enemies. However, the lycaenid subfamily Miletinae is exceptional in its relationship to both ants and Homoptera. Miletine larvae are carnivores of ant-tended homopterans, yet lack the secretory organs crucial to myrmecophily in other lycaenids. This raises questions of how miletines have invaded the ant-homopteran symbiosis, and how ants affect miletine larval success. Here I address these questions through a study of the only New World miletine, Feniseca tarquinius. I present evidence that chemical camouflage enables F. tarquinius caterpillars to go undetected by ants, and that caterpillars may benefit from the presence of ants. Gas chromatographic analysis of cuticular extracts indicated that F. tarquinius caterpillars bear a cuticular hydrocarbon profile similar to that of its aphid prey, and that the profile varies with prey species. Bioassays in the field confirmed the behavioral relevance of the extracts analyzed. Field censuses of 98 caterpillars in 2001 suggested F. tarquinius larvae benefit from the presence of some ant species. Caterpillars in the 2nd through 4th instars were less likely to conceal themselves under silken webs if the ants Camponotus pennsylvanicus or Formica obscuriventris were tending the aphid prey, and pupation rate was greater in the presence of C. pennsylvanicus than in the absence of ants. These effects were not, however, reproduced by 11 pairs of caterpillars in an ant exclusion experiment in a screened garden in 2002.
Key words: Miletinae, chemical camouflage, Lycaenidae, aphytophagy