Formicoxenus chamberlini

This ant is found in the nests of Manica invidia in Utah.

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

Biology
Wheeler (1904) - In thirteen of the workers minute ocelli are present, although sometimes only the anterior median ocellus is represented. As there were many fine males and virgin females of the Manica invidia in the nest, it is probable that the habits of Formicoxenus chamberlini are similar to those of the European Formicoxenus nitidulus and the American Formicoxenus provancheri. The Formicoxenus probably have their own independent nest in the midst of the Manica formicary, but consort freely with the host ants. Confirmation of this view is contained in the following notes kindly sent me by Mr. Chamberlin: "Nests of Manica invidia are common in some localities near Salt Lake City over the flood-plains of the Jordan River. The soil where they occur oftenest is prevailingly argillaceous and sometimes contains much 'alkali:' I have not found them in stony or gravelly ground. All the nests observed opened free from any cover, and not a few were seen in the middle of foot-paths, although they prefer loose soil. In several parts of a ten-acre field where the soil is of the usual character I found nests of this Manica containing the symbiotic species. Three of these compound colonies were preserved, two now being in a collection stored at my home in Utah, the other being the one you have examined. I never succeeded in finding one of the compound nests elsewhere than in this particular field. My attention was drawn to the first compound nest by seeing two individuals of Formicoxenus disappear into a burrow immediately following a Manica worker. Upon excavating I found others of the symbiotic form, mostly collected in a chamber about eight inches below the surface of the ground. The nest seemed to be above the average in size."

Nomenclature

 *  chamberlini. Symmyrmica chamberlini Wheeler, W.M. 1904a: 5, pl. 1, figs. 1-7 (w.q.m.) U.S.A. Combination in Formicoxenus: Francoeur, Loiselle & Buschinger, 1985: 379. See also: Buschinger & Francoeur, 1983: 297.

Worker
Length 3-3.25 mm.

Antennal scape reaching to half-way between the eye and the posterior corner of the head. Epinotal spines short and acute, hardly longer than broad at their bases, shorter than the distance which separates them, directed upward and backward. Petiole from above oblong, with subparallel sides, about 1 1/2 times as long as broad; node in profile rather conical, transverse, but not very high, both its anterior and posterior slopes concave, the former somewhat longer than the latter; lower surface with a median keel ending anteriorly in a blunt tooth. Postpetiole half as broad again as the petiole, distinctly broader than long, with rounded anterior angles, constricted behind at its juncture with the gaster; in profile evenly convex on the dorsal, somewhat flattened on the ventral surface.

Mandibles, head, thorax, petiole, and postpetiole opaque. Clypeus, frontal area, gaster, and legs shining. Mandibles coarsely punctate. Clypeus longitudinally rugose except in the middle; this and the interrugal spaces with shallow punctures. Head rather coarsely and densely, longitudinally reticulate-rugose, with punctate-rugose interrugal spaces. Thorax reticulate-rugose, very finely and irregularly on the pro- and mesonotum, much more coarsely on the pleurae and epinotum. As in the head, the coarser rugae enclose minor reticulations. Petiole and postpetiole uniformly rugose-punctate. Antennae and legs covered with coarse, piligerous punctures.

Excepting the lower surfaces of the thorax and pedicel, the body as well as the legs and antennae are covered with abundant, coarse, suberect, yellow hairs, which are longest on the body, especially on the pedicel and gaster, and shorter and somewhat more reclinate on the appendages. There is no pubescence.

Rich ferruginous red throughout, gaster and legs somewhat paler than the head, thorax, and pedicel.

Queen
Length 3.25 mm.

Differing from the worker in the sculpture of the thorax: the mesonotum, paraptera, and scutellum being subopaque and rather finely, longitudinally rugose, the mesonotum smooth in the parapsidal and midanterior regions, which are also of a paler color than the remainder of the thorax. Prothorax, pleural, and epinotum very coarsely reticulate- rugose. Epinotal spines of about the same size and shape as in the worker.

Male
Length 3-3.25 mm.

Epinotal spines reduced to two obtuse swellings. Petiole nearly twice as long as broad, the anterior portion, seen from above, somewhat more slender than in the worker, without a ventral tooth, and with the node rounder. and lower.

Sculpture, pilosity, and color like those of the worker, with the following exceptions: Scutellum and parapsidal regions of mesonotum smooth and shining; bottom of mesoepinotal constriction with several prominent longitudinal rugae; upper surface of postpetiole smoother, and upper surface of epinotum finely reticulate-rugose like the pedicel. Legs with somewhat sparser hairs. Head darker than the remainder of the body; ocellar region black. The cephalic rugae are denser and sharper around the ocelli, from which they tend to radiate.

Type Material
Described from twenty-one workers, five males, and a single female taken Aug. 20, 1902, near Salt Lake City, Utah, in a flourishing colony of Myrmica mutica Emery (=Manica invidia) by Mr. C. V. Chamberlin.