Mixed Colonies in Ants: Third Report

There are two species of ants with deep clypeal fossae, belonging to the rufa group of the genus Formica, found in the region around the Iowa Lakeside Laboratory in northwestern Iowa. One of these, Formica fossaceps Buren, is almost hairless, especially on the dorsal surface, while the other, Formica obscuriventris clivia Creighton, is very hairy all over, with hairs even on the scapes. The latter species was reported erroneously as Formica areas comptula Wheeler in our earlier papers on mixed colonies (King, \u2749; King and Sallee \u2751). We have recorded large worker ants with vestigial wings in both species, and have compared the winged workers with normal workers and females in the two species (King and Sallee, \u2752; King, \u2755). Since there is a bare possibility that these two nominal species may represent two forms of a single dimorphic species, clivia will be referred to as hairy, and fossaceps as hairless. Whatever the final decision the two forms are readily separable in the workers, females and males. During the last 11 years nearly forty-one thousand ants have been examined as follows: in 40 pure colonies of hairless, 5,847 workers, 154 females and 168 males; in 16 pure colonies of hairy, 5,049 workers, 220 females and 70 males; in 15 mixed hairy-hairless colonies, 25,902 workers, 889 females and 2,654 males. As will be apparent later one may never be sure that a pure hairless colony will not turn out to be mixed until sexual forms, especially males, have been collected from that nest