Intercaste, intercolony, and temporal variation in cuticular hydrocarbons of Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae)

We characterized the variation in cuticular hydrocarbon mixtures between seven colonies of the Formosan subterranean termite, Coptotermes formosanus Shiraki, from the same population. We report differences between castes, between colonies, and within the population over time to assess seasonality. Colonies of C. formosanus from Oahu, Hawaii, were sampled for 25 months. Each month, one sample each of 200 workers, 50 soldiers, nymphs, or elates from each colony was subjected to gas chromatography-mass spectrometry (GC-MS) analysis of the cuticular hydrocarbons. We resolved 39 individual peaks and identified 52 individual or isomeric mixtures of hydrocarbons. Only n-alkanes and methyl-branched alkanes occur; no olefins were found. Internally branched monomethylalkanes were the most abundant class of hydrocarbons, representing 45% to 50% of the total. 9-;11-;13-Methylheptacosane accounted for over 30% of the total hydrocarbon for all castes. 2-Methyl- and 3-methylalkanes comprise approximately 30% of the total. Internally branched dimethylalkanes constitute 15% to 20% of the total cuticular hydrocarbon. Only one trimethylalkane, 13,15,17-trimethylnonacosane, was found in small amounts. The hydrocarbon mixtures of all four castes were similar. Quantitative differences in hydrocarbon mixtures among the castes were easily displayed using canonical discriminant analysis. Soldiers and workers are significantly different from one another and from nymphs and elates. Nineteen peaks are statistically significant between workers and soldiers. Nymphs and elates were not statistically different. We detected statistically significant quantitative differences between colonies in 18 peaks for workers and 12 peaks for soldiers. Each of the colonies of C. formosanus can be separated from the others by the proportions of their hydrocarbon components. We detected statistically significant differences between months of the year for 12 peaks for workers and four peaks for soldiers; two peaks each for workers and soldiers showed distinct, seasonal trends. This seasonal shift in proportions of hydrocarbons correlates with the production of alates.