Cuticular hydrocarbons determine sex, caste, and nest membership in each of four species of yellowjackets (Hymenoptera: Vespidae)

Cuticular hydrocarbons (CHCs) of social insects have typically been studied for their roles in reproductive signaling (i.e., fertility) rather than sexual signaling (i.e., interest in mating), resulting in little information about CHCs of males and virgin females. This dearth of information applies particularly to social wasps. We tested the hypothesis that CHCs differentiate sex, caste, and nest membership in each of four yellowjacket species (baldfaced hornets, Dolichovespula maculata ; southern yellowjackets, Vespula squamosa ; western yellowjackets, V. pensylvanica; V. alascensis ). Cold-euthanized queens (21), gynes (81), workers (125), and males (77) from 35 nests were extracted with pentane, and each of the resulting 304 extracts was analyzed by gas chromatography (GC) and GC–mass spectrometry to identify and quantify CHC constituents (aliphatic alkanes and alkenes; mono-, di-, and tri-methyl-branched alkanes). To determine whether caste and sex differ in CHC profiles of wasps, linear discriminant analyses were performed, using Z -transformed relative CHC peak areas as predictor variables and sex and caste, or nest, as grouping variables. When caste and sex were used as a grouping variable, plots of the first two discriminant functions revealed that wasps from each of the four species clustered into their respective groups (queens, gynes, workers, males), with significant differences in group centroids, as measured by Wilks’ lambda. When nest was used as a grouping variable, plots of the first two discriminant functions revealed that workers from each of the four species and males from each of three species (insufficient sample size for V. pensylvanica ) clustered according to nest. Diagnostic power calculations show greater inter-caste than inter-nest variation. Our data support the above hypothesis and inspire future studies to determine the definitive role(s) that gyne- and male-specific CHCs play in the context of sexual communication, from the perspective of both males and females.