Analysis of Beetle Cuticular Hydrocarbons

The insect cuticle, commonly known as the exoskeleton, consists of two layers: a bottom layer called the procuticule and a thin outer waxy coating called the epicuticle. The epicuticle contains hydrocarbons that prevent desiccation and are used for chemical communication both inter- and intra- specifically. For some insects, these compounds are important sociochemicals involved in recognizing nestmates and predators as well as identifying the sex of other insects. The established procedure to extract cuticular hydrocarbons is lethal, directly introducing the insects to toxic solvents. The goal of this study is to develop a non-lethal procedure to extract the cuticular hydrocarbons from forked fungus and carabid beetles, and to identify the extracted components. In the long term, an examination of the cuticular hydrocarbon profiles of beetles may have important biological implications including differences based on sex, fungus species they feed on, and colonies they inhabit. Each beetle was sampled using the developed non-lethal procedure that uses C₁₈ and the established lethal procedure that uses hexane. The results of the C₁₈ procedure were compared to the results of the established solvent extraction to see if the developed procedure was as efficient as the established technique. The samples where analyzed using a Gas Chromatography-Mass Spectrometry (GCMS) instrument. Standard compounds were analyzed to identify some of the components of the cuticular profile. Both procedures extracted the same compounds. Five components of the cuticular waxes were identified including four n-alkanes and one alcohol. The identified compounds are nonadecane, eicosane, heneicosane, docosane, and 1-eicosanol. Chlaenius cordicollis was found to contain all five components, while forked fungus beetles were found to contain nonadecane, eicosane and heneicosane. The differences in the components identified for the two different species of beetles suggests that there is variation in the components of cuticular waxes amongst different species as expected. Previous studies have found that n-alkanes, the majority of extracted components in this study, are primarily involved in the prevention of desiccation and not as sociochemicals. Unlike n-alkanes, alcohols have been shown to function as sociochemicals