Rove beetle cuticular hydrocarbons and nestmate recognition in colonies of the velvety tree ant

Ants shape many of the ecosystems in which they are found, consuming and sequestering a large fraction of the available food resources as well as preying on other arthropods. This pressure over the past hundred million years has resulted in numerous arthropods forming symbiotic relationships with ants, allowing them to avoid predation from the ants as well as giving them access to the resources of the ant colony. To counteract this process of infiltration by non-nestmates as well as to maintain overall nest cohesion, ants exapted cuticular hydrocarbons, used by all insects to prevent against desiccation, for nestmate recognition pheromones. Any organism that lacks the colony cuticular hydrocarbon profile is recognized as foreign and dealt with accordingly. This stringent nestmate recognition system has been sidestepped by numerous myrmecophiles, including those found in the nests of the velvety tree ant, Liometopum occidentale. The rove beetles Sceptobius lativentris and Platyusa sonomae both mimic the CHC profile of their host ant, thus reducing, and in some cases entirely avoiding, detection within the colony. Using a combination of chemical ecology, behavioral techniques,  and fluorescence microscopy we analyzed the CHCs and CHC synthesis enzymes in the two beetle species to identify the mechanisms by which the beetles obtain their CHC profiles. We found that the beetle Sceptobius lativentris steals most of its CHCs from Liometopum via a specialized grooming behavior whereas the beetle Platyusa sonomae synthesizes a large fraction of its CHCs. These beetles represent two disparate mechanisms of convergence on a complex chemical phenotype.