The Sensation and Perception of Cuticular Hydrocarbons in Ants and Termites

Animal groups, and in particular social insects, rely on communication to carry out a common goal. To understand animal communication it is vital to understand what information animals can sense. A large body of evidence suggests that cuticular hydrocarbons play a prominent role as a medium of information within a social insect colony. However, which components of the profile are relevant is not yet clear. It is also not apparent if these compounds are a conserved source of information across social insect taxa. In this dissertation, I investigated the olfactory capabilities of two distinct social insect groups to examine whether cuticular hydrocarbons are equally important across social insects and how the properties of hydrocarbons influence perception. In Camponotus floridanus, I measured electrophysiological responses to and assessed discrimination of hydrocarbons. C. floridanus workers sensed all the compounds tested, including hydrocarbons that do not occur naturally in their environment, and were able to distinguish structurally similar hydrocarbons. I established the hydrocarbon olfactory ability for Zootermopsis nevadensis by measuring antennal responses and confirmed the electrophysiological data with an assay that modifies cuticular hydrocarbons. Z. nevadensis do not detect linear alkanes but do sense two reproductive alkadienes. Concordantly, nestmates have strong reactions to both alkadienes suggesting that these compounds are involved in reproductive communication. Finally, I assessed how volatility impacts hydrocarbon perception. I administered a concentration curve of three alkanes of varying weight to C. floridanus antennae. Additionally, I tested whether ants could detect hydrocarbons at a distance. Ants had roughly similar sensitivities to all three alkanes and were able to detect each without direct antennal contact, suggesting that C. floridanus antennal systems evolved to identify hydrocarbons at a distance. This work builds upon previous findings investigating ant hydrocarbon perception. I show that not only are ant antennae finely tuned to discriminate hydrocarbons but that this extends over small distances, which has important implications for communication. In contrast, I elucidate the sensory capabilities of a termite by showing that they are greatly reduced compared to ants, indicating that there are alternative means of chemical communication in social insects.