Contact cuticular hydrocarbons act as a mating cue to discriminate intraspecific variation in Altica flea beetles

Contact cuticular hydrocarbons (CHCs) are one of the major cues that allow many insects to identify interspecific and intraspecific variation between individuals, and often have mutually nonexclusive functions that can provide multiple types of signals. A previous study showed that two sympatric, closely related Altica beetles achieve behavioural isolation via species-specific CHC profiles. Here, we explored whether these CHCs also play a role in recognition of intraspecific variation. Specifically, we tested the hypothesis that differences in CHCs are a critical mating cue that allows males to discriminate the sex and age (sexual maturity) of females. We used CHC profile analysis and behavioural assays to examine mating cues in three closely related flea beetles, Altica cirsicola, Altica fragariae and Altica viridicyanea (Insecta: Coleoptera: Chrysomelidae). The results showed that (1) CHC profiles are sex and age specific, (2) male beetles can distinguish males from females and can also distinguish sexually mature females from immature ones and (3) CHCs are only one component of mate discrimination as additional cues also appear to be involved.