Stealth and reproductive dominance in a rare parasitic ant

Abstract

Social insects that have secondarily lost the worker caste are the ultimate social parasite; they allocate their energy to sexual production and, thus, rely completely on the host for survival. Most inquiline species are rare, and little is known about their life histories except that they are completed within the host colony. Here we report intracolonial dynamics of the workerless inquiline, Temnothorax minutissimus, which parasitizes T. curvispinosus in eastern North America, and examine cuticular chemicals that may be important for inquiline integration into host society (nestmate recognition) as well as reproductive dominance. We found that autumn colonies frequently contained multiple inquilines, of which only one or two were reproductively dominant and groomed the dorsal side of the host queen's head. Inquilines on the nest periphery or that roamed the foraging arena were young gynes that had not yet dispersed. A large proportion of inquilines were inseminated, but only a few showed evidence of reproduction, none of which were peripheral inquilines. Inquilines differed chemically from one another with respect to behaviour and ovarian development. Groomers resembled host queens chemically and had greater quantities of cuticular chemicals than did peripheral inquilines. Host queens differed little in cuticular chemistry regardless of inquiline attention. Our findings suggest an association between inquiline cuticular chemistry and behavioural activities that reflects ovarian activity. These differences suggest a dual-chemical strategy of inquilines to reside in the host colony: reproductive inquilines mimic the host queen, whereas dispersers maintain a neutral chemical signature.