QUANTITATIVE VARIATION IN CHEMICAL DEFENSE WITHIN AND AMONG SUBGENERAOF CICINDELA

The pygidial secretions of more than 40 species of adult Cicindela wer e quantitatively assayed by gas chromatography and mass spectrometry f or the presence of benzaldehyde, the major defensive compound of cicin delids. All species showed evidence of benzaldehyde secretion, with th e range in benzaldehyde spanning three orders of magnitude. Subgenera, species, and subspecies all accounted for a significant portion of th e total variation in benzaldehyde secretion, while populations within subspecies sampled at different localities did not vary significantly; thus phylogenetic analyses of benzaldehyde secretion within and among both species and subgenera would be appropriate, The evidence suggest s that a single origin of the pathway producing benzaldehyde occurred in the ancestors of Cicindela spp. and that differences among taxa in the amount of benzaldehyde secreted are the result of changes in that pathway's regulation.