Temnothorax tricarinatus

Nests are small, normally with fewer than 100 workers, and are found under rocks and in moist soil in open grassy areas. This includes foothill meadows, sagebrush, shortgrass prairie, pasture and numerous forest habitats (deciduous canyon, oak woodland, oak hickory, cedar and ponderosa pine), especially in gaps or similar open areas (Gregg 1963, Wheeler and Wheeler 1963, DuBois 1985, MacKay et al. 1988, MacKay 2000).

Identification
Mackay (2000) - A member of the Temnothorax tricarinatus species complex. Antenna 12-segmented, antennal scape nearly reaching occipital corner, clypeus with well developed carinae, including a medial carina and two lateral carinae, area between carinae mostly smooth and shining, dorsum of head rugulose, intrarugal spaces shining, area around eye with nearly foveolate punctures, dorsum of mesosoma finely rugulose, with a nearly smooth back ground, side of mesosoma rugose, propodeal spines well developed, length about half distance between bases of spines, subpetiolar process moderately well developed, apex blunt, node of petiole moderately sharp, top of node obliquely truncate, top of petiole and postpetiole with rugae, background surface smooth, dorsum of gaster shiny.

Temnothorax tricarinatus could be confused with several other species, especially Temnothorax stenotyle, and Temnothorax rugithorax. It can be separated from Temnothorax stenotyle as the postpetiole is noticeably widened when compared with the petiole. The head is much more coarsely sculptured, with coarse rugae, whereas the head of Temnothorax rugithorax is more finely sculptured, with fine rugulae, and even some areas that are nearly smooth and shining. Specimens of Temnothorax rugosus with a lightly sculptured gaster may key here. They differ in being much more coarsely sculptured, with coarse rugae on the head and dorsum of the mesosoma. The petiole is broader and not laterally "pinched" as it is in Temnothorax rugosus. The clypeus of Temnothorax tricarinatus has the medial and 2 lateral clypeal carinae well developed, whereas they are not much more developed than any of the other carinae in Temnothorax rugosus.

Distribution
United States: North Dakota, South Dakota, Idaho, Wyoming, Utah, Nevada, Arizona, Colorado, New Mexico, Nebraska, Iowa.

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

Habitat
Occurs in open habitats such as grasslands and open forest.

Abundance
Infrequently collected.

Biology
Smith (1952) "Buren records the form as nesting in the ground in small colonies in at least two localities in Iowa. Severin in South Dakota has collected specimens from alkali fiats and the Badlands. He has also taken individuals while sweeping various grasses and weeds at Canning. At Greeley, Colorado, the ants were collected from a bean field, and at La Junta from a region bearing the Russian thistle, Salsola pestifer Nels. The food of the workers is not known, but it probably comprises small arthropods supplemented by honeydew. In South Dakota males have been collected in various localities from July 26 to September 14."

Nests can contain either a single queen (monogynous) or multiple queens (polygynous).

Nomenclature

 *  tricarinatus. Leptothorax (Leptothorax) tricarinatus Emery, 1895c: 321, pl. 8, fig. 14 (w.) U.S.A. Smith, M.R. 1952b: 99 (m.). Combination in L. (Myrafant): Smith, M.R. 1950: 30; in Temnothorax: Bolton, 2003: 272. See also: Wheeler, W.M. 1903c: 247; Mackay, 2000: 417.

Worker
Fusco-nigra, mandibulis, articulationibus pedum et tarsis 1'ufescentibus, clavato pilosa, scapis pedibusque subnudis; capite, thorace pedunculoque subopacis, punctatis et subtiliter rugatis, pronoto medio nitidiore, clypeo nitido, antice medio obtuse angulato, superne carinis tribus subtilibus longitudinalibus instructo, mandibulis striatis, antennis 12articulatis, articulo funiculi primo tribus sequentibus una majore, reliquis brevioribus quam crassioribus, clavae articulis duobus primis subaequalibus; thorace haud impresso, metanoto spinulis brevibus, seu dentibus acutis oblique erectis, pedunculi segmento 1. postice incrassato, superne cum eminentia subconica, obtusa, 2. multo majore, subgloboso. Long. 2 1/4 mm.

(Smith 1952)WORKER.-Length 2-2.6 mm. Head sub rectangular, distinctly longer than broad, with almost straight posterior border, rounded posterior corners and weakly convex, somewhat subparallel sides. Antenna 12•segmented; scape lacking approximately its greatest width of reaching the posterior border of the head; funiculus with a distinct 3-segmented club, the last segment of which is clearly longer than the combined lengths of the two preceding segments; first funicular segment approximately as long as the three succeeding segments. Eye oval, rather prominent, situated approximately its greatest length from the base of the mandible. Clypeus with a distinct shield or plate at the middle of its anterior border, which usually bears a distinct median and two lateral, longitudinal carinae; each side of the shield commonly bearing a number of smaller and less distinct longitudinal carinae. Frontal area poorly defined or obsolescent. Mandible of the usual shape, with five teeth, of which the apical is the largest. Thorax in profile, moderately convex; from above, widest at the well-rounded prothoracic humeri, narrowest laterally in the region of the mesoepinotum, dorsal surface without sutures or a mesoepinotal impression. Epinotum bearing a pair of short, dentiform or tuberculiform spines. Dorsal portion of petiolar node in profile forming an obtuse angle or else a weakly developed subrectangle. Postpetiolar node from above, large, transverse, but not twice as wide as the petiolar node; approximately 1 1/2 times as broad as long, with almost straight anterior border, rounded anterior shoulders and weakly convex, somewhat subparallel sides. Gaster from above, oval, with angular humeri.

Head, thorax, petiole and postpetiole subopaque or opaque; clypeal shield, frontal area and gaster rather smooth and shining. Mandible longitudinally striated, the surface bearing scattered, piligerous punctures. Dorsal surface of head largely punctate or granulate, but also with a number of delicate rugulae extending from the clypeus toward the occiput; cheek, and region between the eye and the frontal carina largely rugulose or rugulose-reticulate. Dorsum of thorax distinctly but not extraordinarily coarsely rugulose or rugulose-reticulate, the sculpturing usually less coarse on the mesonotum than on the pronotum and epinotum. Petiolar node rugulose-reticulate. Postpetiolar node usually finely punctulate or granulate, occasionally finely rugulose-reticulate in addition.

Body with rather abundant, well scattered, coarse, grayish or whitish, sub erect to erect hairs. Hairs on the leg similarly colored but smaller and more appressed; coxa, trochanter and femur with a few scattered, sub erect to erect hairs. Scape with fine, rather dense, appressed pubescence. Pubescence of gaster composed of distinct but sparse, well scattered, appressed pile.

Dark brown to brownish black but not jet black; mandible, base of each funiculus, pronotal collar, apex of coxa, trochanter, base of femur, tibia and articulations of leg lighter.

Queen
Queens are variable in size.

Male
(Smith 1952) MALE.-Length 1.8-2 mm. Head, including eyes, broader than long, with rounded posterior border and rounded posterior angles. Eye large, strongly convex, protuberant, situated approximately one-fourth its length from the base of the mandible. Ocelli small, arranged in a triangle on the vertex of the head but scarcely protruding above the general surface of the head. Clypeus convex in the middle, lacking the characteristic shield or plate of the worker. Mandible rather small, sub triangular, with an apical and several less distinct teeth. Antenna 13-segmented; last 4 funicular segments forming a well defined club, the apical segment of which is longer than the combined length of the 2 preceding segments; scape rather stout and short but longer than the space between the frontal carinae; first funicular segment pyriform. Mayrian furrows lacking or obsolete on the thorax, the parapsidal sutures present but not easily discernible. Anterior wing pale grayish or whitish; veins pale and rather indistinct, usually forming a closed cubital and a discoidal cell, the discoidal cell however sometimes poorly developed or lacking; stigma well developed but indistinct because of its pale color. Epinotum in profile, subangular, bearing a pair of weak longitudinal carinae or else a pair of indistinct tooth-like protuberances. Leg rather long and slender, with slightly enlarged femur and tibia. Postpetiolar node from above, subcampanulate, not twice as wide as the petiolar node. Gaster from the same aspect, oval. Stipes stout, bluntly sub triangular.

Much of the body with finely punctulate or granulate sculpturing; scutellum, mesopleuron, dorsal surface of petiolar and postpetiolar nodes and gaster, smooth and shining.

Pilosity similar to that of the worker but apparently not so abundant, long or coarse.

Color similar to that of the worker but even darker; the mandible, pronotal collar and articulations of the leg not as light or as contrastingly marked.

Type Material
Mackay (2000) - Hill City, South Dakota. Holotype worker, [seen]."

Etymology
Morphology. The clypeus has a well developed medial and two lateral carinae.