Original Article

Imperfect chemical mimicry explains the imperfect social integration of the inquiline ant Ectatomma parasiticum (Hymenoptera: Formicidae: Ectatomminae)

Savarit, F. & Fénéron, R.

Abstract: Inquilinism is an extreme form of social parasitism where the parasite permanently depends on its host. This parasitism is widespread among Formicinae and Myrmicinae ants but rare in other subfamilies, like Ectatomminae where Ectatomma parasiticum Feitosa & Fresneau, 2008 is the sole inquiline described so far. This species is genetically and morphologically very similar to its host, E. tuberculatum (Olivier, 1792), and uses its worker force to produce exclusively sexuals. During their life cycle, E. parasiticum queens enter into established host colonies and cohabit with the resident queens over an extended period of time. However, previous experiments in the laboratory have shown that some parasites are attacked by host workers, suggesting that their social integration into host colonies is incomplete or unstable. We thus investigate how the chemical cues of the parasites relate to the host's recognition system. For this, we compare the cuticular hydrocarbon profiles of parasites, host queens and host workers using solid-phase microextraction. Although overlapping, the chemical profiles of both species are distinct. Parasites have no specific compounds but a reduced total amount of cuticular hydrocarbons compared with hosts. We suggest that E. parasiticum uses an imperfect chemical mimicry strategy as it is well-discriminated by its host species.