Formica fossaceps

Buren (1942) reported the type material was collected from a nest that was "located around the base of a bush, plant debris being used in the construction of a low dome. Immediately under this dome were the brood, workers, and sexual forms.

Identification
This species seems definitely related to Formica rufa and its numerous subspecies and varieties. It differs from all of them, however, by the paucity of both pilosity and pubescence, the very shining surface, and the depth of the clypeal fossae. Formica obscuriventris seems to be most closely related in the structure of the clypeal fossae and the funiculi. F. fossaceps can be distinguished from obscuriventris by the smaller size of the female, the more shining surface of both female and worker, the deeper clypeal fossae, the more bead-like funicular joints, the ecarinate clypeus, and by the lack of pilosity on the dorsal surfaces of both female and worker. In addition fossaceps has a somewhat differently shaped head. (Buren 1942)

Distribution based on Regional Taxon Lists
Nearctic Region: Canada, United States.

Nomenclature

 *  fossaceps. Formica fossaceps Buren, 1942: 402 (w.q.m.) U.S.A.

Worker
Length, 6.65-7.71 mm.

Head, excluding the mandibles, slightly longer than broad, narrower in front than behind, with feebly excised or straight posterior border and nearly straight sides. Clypeus evenly rounded in front, ecarinate or distindly carinate only at the extreme front. Clypeal fossae strikingly deep; antennal fossae also rather deeply impressed. Maxillary palpi short. Apex of frontal area rounded. Frontal carinae diverging, about twice as long as the diameter of the antennal foramina. Frontal furrow indistinct, ending in a shallow pit level with the eyes. Eyes hairless. Scapes surpassing posterior lateral corners of the head by nearly two-fifths of their length. Funicular joints gradually decreasing in length toward the penultimate, the second approximately four-fifths as long as the first and about one-third again as long as the penultimate, the third slightly shorter than the second; joints 5-8 rather unusual in appearance, each narrow at the base but swollen to more than 1% times the base width near the apex. To the naked eye these joints are somewhat bead-like.

Pro- and mesonotum not as convex as in Formica obscuriventris. Meso-epinotal depression not as deep. Epinotum in profile with subequal base and declivity, the base slightly convex, the declivity feebly concave. Petiole large, higher than the epinotum, in profile cuneate, the superior border very sharp. Seen from behind, the petiole broad, measuring up to. 77 mm. wide, and strongly subangularly or convexly produced upward.

Head and legs moderately shining, gaster more shining but not as highly polished as that of the female, the shagreening on the gaster very fine and superficial. Thorax subopaque.

Erect hairs absent on most body surfaces, present on the dorsum of gaster near the apex, venter of gaster, venter of petiole, and coxae. Pubescence very short and sparse. especially on the head and gaster, rather dense only on the base of gaster, petiole, epinotum and appendages. Head and thorax ferruginous, appendages brown, entire gaster deep black.

Media Worker

Length, 5.23-6.62 mm. ..

Differing from the major in having the head straight or slightly convex behind, the clypeal fossae a little less deep, the basal funicular joints shorter in proportion to the penultimate, the middle joints less bead-like, and the head and thorax often infuscated.

Minima Worker

Length, 3.70-4.58 rom.

Differing from the major in having the head definitely longer than broad and slightly convex behind, the clypeus distinctly carinate, the clypeal fossae more normal in depth, funicular joints 2-10 more nearly subequal in length, and the middle joints not bead-like. Also differing in having the body a little less shining and the head and thorax heavily infuscated.

Queen
Length, 7.19-7.84 mm.

Although little shorter than the females of Formica obscuriventris, strikingly more slender and much less massive than this species.

Head, including the mandibles, triangular in shape; the outer borders of the mandibles nearly aligned with the sides of the head; excluding the mandibles, slightly longer than broad (about 1.38mm. wide), one-third again as wide behind as in front, with straight posterior border and sides. Clypeus evenly rounded in front, ecarinate. Clypeal fossae extraordinarily deep, the middle part of the clypeus between them strongly convex in transverse section. Frontal carinae diverging, approximately twice as long as the diameter of the antennal foramina. Frontal furrow very short and indistinct, not reaching beyond the frontal carinae. Funiculi much as in the major worker, but joints 5-8 not as bead-like and the second joint only a little shorter than the first. Eyes hairless, a little larger than those of the worker. Thorax narrower than the head about 1.2 mm. wide. Petiole large, cuneate in profile, with sharep superior border, subangularly produced upward when seen from behind.

Entire body, especially the gaster, glaborous and extremely smooth. Thorax a little less shining than the head and gaster. Shagreening on the gaster scarcely perceptable, the surface marked only by the very sparse, minute punctures from which the pubescence arises.

Pilosity entirely lacking on all dorsal regions of the body body; some slender, scattered hairs on the ventor of the gaster and coxae. Pubescence very fine, short, and sparse, about .01-.02 mm. in length, rather dense only on the base of the gaster and appendages, extremely parse on the head.

Head and thorax light brownish red. Gaster entirely deep black except at the extreme base. Head lightly infuscated behind the eyes. Mesonotum heavily infuscated in a median frontal spot and along the parapsidal sutures. Scutellum and metanotum black.

Male
Length, 8.06 mm.

Head, excluding the mandibles, distinctly broader than long, much broader behind than in front. Mandibles feebly 3-toothed. Clypeal fossae very deep. Funicular joints 2-10 gradually decreasing in length, the penultimate a little over one-half as long as the second, the second one-fourth again as long as the first. Petiole in profile, with convex anterior and flat posterior surfaces; seen from behind, subrectangular, the superior border sinuate but nearly truncate, the sides almost straight.

Head and thorax mainly opaque, the declivity of the epinotum glabrous; gaster feebly shining.

Erect hairs nearly absent on the dorsal surfaces of the body, a few on the gula, profuse on the venter of the gaster toward the apex. Pubescence sparse, but longer and much denser than in the worker and female.

Color black, the antennae dark brown, legs light brown.

Type Material
Described from 12 females, 93 workers, and 1 male taken from a nest in wooded pasture near Winterset, Iowa, June 27, 1941.