FUNCTIONAL MONOGYNY IN THE AMERICAN GUEST ANT FORMICOXENUS-HIRTICORNIS (EMERY) (=LEPTOTHORAX-HIRTICORNIS), (HYM, FORM)

12 samples of Formicoxenus hirticornis (Emery) were collected from 4 Formica obscuripes nests in the Yellowstone Park, Wyoming, in August, 1977. The dealate females and intermorphs, and some workers were dissected. All 16 females and 13 of the 16 intermorphs were inseminated, but only 10 females and 4 intermorphs were egg-laying. It seems that each colony normally contains only one fully fertile specimen, and a few additional, inseminated but sterile females or intermorphs. These results are very similar to our observations on the European guest-ant Formicoxenus nitidulus (Nyl.). We conclude that F. hirticornis (and maybe the closely related F. diversipilosus, too) is functionally monogynous like F. nitidulus and Leptothorax gredleri Mayr, which means that supernumerary inseminated females and intermorphs are accepted in queenright colonies, but they are kept sterile by a mechanism which is not yet known. Leptothorax hirticonis Emery and L. diversipilosus M.R. Smith in my opinion belong to the genus Formicoxenus, since they have, together with F. nitidulus, a number of unique, common characters: The males of all three species are wingless and workerlike, they all live as guest ants in the mound nests of Formica species, and they have a peculiar female polymorphism with both dealate and intermorphic queens besides normal workers. © 1979 Masson.