Camponotus castaneus

Widely distributed through the eastern half of the US, C. castaneus seems nowhere to be common except, perhaps, in the South Atlantic states. It forms moderately populous colonies, which nest in the ground under stones in open woods, in the same manner as the species of the Camponotus-maculatus group. The workers are very timid and probably nocturnal. (Wheeler 1910)

Identification
A single-colored (concolorous), orange to chestnut-brown ant; in full-face view, a ridge (median carina) may be visible on the clypeus; no erect hairs on the cheeks.

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

Fungi
Mangold et al. (2019) studied the mechanistic details of how the fungus infects its worker hosts and causes the ants to clamp their mandibles onto a leaf with a so called death grip. This anchoring attaches the dying worker to the vegetation, which in turn allows the fungus to develop its spores in a location where their release will occur over and thus onto the forest floor below. This study found the fungus builds and penetrates around cells and tissues of the ant's mandibular muscles to produce its death grip. Motor neurons and neuromuscular junctions did not show any evidence of being effected or attacked by the fungus.

Nomenclature

 *  castaneus. Formica castanea Latreille, 1802c: 118, pl. 3, figs. 11, 12 (w.q.m.) U.S.A. Wheeler, W.M. 1910d: 321 (s.). Combination in Camponotus: Roger, 1863b: 6; in C. (Camponotus): Forel, 1914a: 266; in C. (Tanaemyrmex): Creighton, 1950a: 375. Senior synonym of mellea (and its junior synonym clarus): Mayr, 1886d: 420; Forel, 1886f: 141.
 * mellea. Formica mellea Say, 1836: 286 (m.) U.S.A. Mayr, 1866a: 485 (w.q.). Combination in Camponotus: Roger, 1863b: 5. Senior synonym of clarus: Mayr, 1866a: 485 (in text). Junior synonym of castaneus: Mayr, 1886d: 420; Forel, 1886f: 141.
 * clarus. Camponotus clarus Mayr, 1862: 660 (w.) U.S.A. Junior synonym of mellea: Mayr, 1866a: 485 (in text).

Worker
Wheeler (1910) - Major Length, 9-10 mm.; head, 3.2 x 2.8 mm.; scape, 3 mm.; hind tibia, 3.4 mm.

Head small, but little broader behind than in front, with rounded sides and feebly excised posterior border. Eyes somewhat convex. Mandibles 6- to 7-toothed. Clypeus convex in the middle, ecarinate or bluntly and indistinctly carinate; its anterior border broadly rounded, not produced, sinuate at the sides, with crenate edge. Frontal carinae lyrate, rather far apart. Frontal area indistinct, extremely small; frontal groove distinct. Antennal scapes rather long, reaching about one-third their length beyond the posterior corners of the head, their bases terete, neither flattened nor dilated, distal ends not incrassated. Thorax slender; laterally compressed, moderately high, in profile rather evenly arched above; epinotum with indistinct base and declivity, the former about twice as long as the latter. Petiole thick, with strongly convex anterior and flattened posterior surface and very blunt" rounded and entire margin. Gaster of the usual form. Legs long; middle and hind tibiae neither compressed nor sulcate, elliptical in cross section.

Whole body shining, very finely and superficially shagreened, more coarsely on the anterior portions of the head. Mandibles coarsely and uniformly punctate. Cheeks with small, slightly elongated foveolae, or punctures; sides of clypeus and front feebly punctate.

Hairs yellow, erect and sparse, very short on the mandibles, rather long on the border of the clypeus, absent on the sides and corners of the head and on the legs and scapes, except at the tips of the latter and of the femora. Middle and hind tibiae with a series of short bristles on the distal half of their flexor surface. Pubescence very short, dilute and indistinct.

Yellow or yellowish red, head and gaster somewhat darker; mandibles, antennal scapes, anterior border of clypeus and cheeks very dark red or blackish; tibiae and tarsi also sometimes brown or dark red. Gastric segments sometimes obscurely brownish posteriorly. Mandibular teeth black.

Minor Length, 7-8 mm.

Head somewhat less than twice as long as broad, sides subparallel, slightly convex, postocular portion rounded, slightly contracted towards the occipital border. Clypeus similar to that of the worker major, but more truncated in front. Antennae long and slender, the scapes reaching nearly 'half their length beyond the posterior corners of the head. Sculpture, pilosity and coloration like that of the worker major.

Queen
Wheeler (1910) - Length, 13-15 mm.

Closely resembling the worker major, but the head has straighter and less convex sides, the petiole is much compressed anteroposteriorly, with a rather sharp border, which is distinctly notched in the middle above, and the color of the whole body is often deeper and more brownish. Wings long (15 mm.), strongly suffused with yellow; veins and stigma brownish yellow.

Male
Wheeler (1910) - Length, 8-9 mm.

Head longer than broad, but little broader behind than in front; cheeks concave, subparallel, about as long as the eyes, which are moderately large. Clypeus convex, but not carinate, with broadly rounded anterior border. Mandibles edentate, rather broad. Thorax robust, epinotum convex, without distinct basal and declivous surfaces. Petiole low, thick, transverse and very blunt above. Gaster, antennre and legs slender.

Sculpture, pilosity and color like those of the female, but hairs shorter and less conspicuous, absent on the cheeks and thorax, except the epinotum, which bears a few erect hairs. Mandibles scarcely darker than the head; mesonotum often streaked with brown. Wings colored like those of the female.

Type Material
Wheeler (1910) - The types of this species, which is easily recognized by the red color of all the phases, came from the Carolinas and Pennsylvania.