Stenamma snellingi

This species is abundant and widespread within its range, tolerating a wide range of conditions. It is typically found in the litter layer in forest habitats.

Identification
This species is highly variable and is closely related to Stenamma diecki. It can be difficult to identify specimens of this species even with a number of specimens from a single nest. A treatment of the key morphological distinctions between these Stenamma snellingi and Stenamma diecki is found in the species account for Stenamma diecki.

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

Biology
Smith (1957): Our records show that males as well as male and female pupae are found in the nest at least as early as late August (25-27). Winged females and males have been captured in flight at Lake Louise near Steilacoom, Washington, on September 21. Other winged females and males have been collected as late as October (29-31), but the conditions under which they were taken are not known; therefore it cannot be definitely said whether these sexed forms were produced during the current year or the year preceding. The species has been collected at altitudes ranging from 700 feet to as high as 9,000 feet. All known colonies are from the soil beneath rocks.

Nomenclature

 * occidentale. Stenamma occidentale Smith, M.R. 1957b: 146, pl. 2, fig. 7 (w.q.m.) U.S.A. (Arizona, California, Oregon, Washington, Idaho, Colorado, New Mexico), CANADA (British Columbia), MEXICO (Baja California).
 * Type-material: holotype worker, 53 paratype workers, 14 paratype males.
 * Type-locality: holotype U.S.A.: Arizona, Chiricahua Mts, Rustlers Park, 8500 ft, 25-26.viii.1952 (B. Malkin); paratypes with same data.
 * Type-depository: USNM.
 * [Junior primary homonym of Stenamma (Aphaenogaster) subterraneum subsp. occidentale Emery, 1895c: 301.]
 * Status as species: Smith, M.R. 1958c: 116; Smith, M.R. 1967: 352; Snelling, R.R. 1973c: 25; Hunt & Snelling, 1975: 21; Yensen, et al. 1977: 183; Smith, D.R. 1979: 1359; Allred, 1982: 506; Wheeler, G.C. & Wheeler, J. 1986g: 34 (in key); Mackay, Lowrie, et al. 1988: 101.
 * Replacement name: Stenamma snellingi Bolton, 1995b: 394.
 * . Stenamma snellingi Bolton, 1995b: 394.
 * Replacement name for Stenamma occidentale Smith, M.R. 1957b: 146. [Junior primary homonym of Stenamma (Aphaenogaster) subterraneum subsp. occidentale Emery, 1895c: 301.]
 * Status as species: Mackay & Mackay, 2002: 239; Ward, 2005: 67.
 * Distribution: Canada, Mexico, U.S.A.
 * [Note: the correct name for this taxon appears to be neoarcticum Mayr.]

Worker
Length 3.4 mm. Funicular segments 2 through 6 broader than long; last funicular segment longer than the combined lengths of the two preceding segments. Eye small, oval, approximately 0.10 mm in its greatest diameter with six ommatidia. Thorax, from above, slender, 1.2 mm in length from the anterior border of the pronotal collar to the junction with the petiole, broadest through the humeral angles (0.45 mm) and narrowest through the epinotum (0.35 mm); with pronounced humeral angles; in profile, the mesoepinotal impression is moderately well developed, approximately 0.10 mm in length and 0.05 mm in depth, base of epinotum distinctly sloping to meet the declivity and form two small, tuberculate spines which are 0.05 mm in length or less. In profile, the petiolar node is subangular; the postpetiolar node larger than the petiolar node and more convex in its anterior half than its posterior half, from above, the postpetiole is stout, almost as broad as long. Gaster with the apex more acute than the base, the latter lacking humeral angles.

Sculpturing of head and thorax very weak, subopaque (in some lights, however, part of the thorax is slightly shining), the head apparently more subopaque than the thorax, the propleuron is sculptured and subopaque and the mesopleuron largely reticulate; epinotal declivity postpetiole and gaster smooth and shining, the dorsal surface of the petiole, especially the anterior face, somewhat shining in some lights.

Hairs light yellowish or grayish depending upon the light, moderately abundant, of variable length, largely depressed or suberect, those on the front of the head and anterior border of the clypeus unusually long. Pubescence of legs and scapes distinct but depressed.

Head, thorax, petiole and postpetiole dark brown, legs and gaster lighter, the latter with a rather broad, infuscated, transverse band near its mid length.

Paratype workers differ from the holotype mainly in the proportions of the head which ranges from 1.15-1.25 times as long as broad; the length of the thorax, 1.05-1.2 mm; greatest width of the thorax, 0.4-0.45 rom; narrowest width of thorax 0.3-0.35 mm; epinotal spines 0.03-0.05 mm in length; mesoepinotal impression 0.03-0.05 mm in depth and the postpetiole from almost as broad as long to apparently as broad as long; length of body 2.8-3.4 mm.

Workers other than paratypes show considerable variation in a number of characters, these variations are: Head 1.12-1.25 times as long as broad; thoracic length 1-1.10 mm, greatest width 0.5 mm; narrowest breadth 0.25 mm; greatest diameter of the eye ranging from 0.05-0.10 mm; mesoepinotal impression varying in size and shape, roughly U- or V-shaped and 0.10 mm long and about half as deep; epinotal spines 0.025 to 0.05 mm in length; pedicel of the petiole noticeably shorter and the petiolar node less high in some individuals than others; pronotum less flattened and without such prominent humeral angles; color ranging from light to dark brown with the anterior portion of the head, antennae, legs and usually the base and apex of the gaster lighter. Although the head, thorax and petiole are usually subopaque and the postpetiole smooth and shining, the former regions may be slightly shining in some lights.

Queen
Similar to the worker except as described below.

Length 4.5 mm. Ocelli small, not very distinct, the anterior ocellus located about 0.4 mm posterior to the frontal area. Antennal scape failing by less than its greatest diameter to attain the posterior border of the head. First funicular segment approximately as long as the combined lengths of the three succeeding segments; last segment of the dub approximately as long as the combined lengths of the three preceding segments. Eye oblong, its greatest diameter approximately 0.20 mm and with 12-13 ommatidia. Thorax 1.6 mm in length from the anterior border of the pronotal collar to the apices of the epinotal spines, widest (0.8 mm) anterior to the points of articulation of the wings. Anterior wing hyaline, with light brown or yellowish veins and stigma and bearing a dosed cubital and discoidal cell but only an open radial cell. Vein r-m present but Mf3 lacking. Epinotal spines, from above, scarcely half as long as the distance between their bases; in profile, short (less than 0.10 mm in length), tuberculate, with the apex of each directed lateroposteriorly but scarcely dorsad. Petiole, in profile, pedunculate, the anterior and posterior faces of the node meeting to form a very distinct angle. Postpetiolar node, in profile, convex above, concave beneath, scarcely higher than long. Petiolar node, from above and behind, with dorsally converging sides and subtruncate superior border. Postpetiole, from above, approximately 0.143 times longer than broad, with anteriorly converging sides in its anterior two-thirds and subparallel sides in the remainder. Gaster, from above, widest near its middle, the first segment occupying most of the gaster.

Mandibles striato-punctate, subopaque in some lights, shining in others. Clypeus, frontal area, area beneath epinotal spines, and much of each mesopleuron largely smooth and shining. Gaster entirely smooth and shining. Head with rather fine, longitudinal rugulae extending posteriorly from the frontal area, the rugulae becoming divergent posteriorly and even attaining the occiput; remainder of the dorsal surface of the head rugulose-reticulate with dull interspaces bearing umbilicate punctures. Cheeks largely longitudinally rugulose. Prothorax transversely rugulose anteriorly and longitudinally rugulose on the sides. Mesonotum and scutellum largely longitudinally rugulose, the interspaces shining, at least in some lights. Mesoepisternum and side of the epinotum longitudinally rugulose, the latter with finely punctulate interspaces. Base of epinotum transversely rugulose, with punctulate interspaces. Posterior surfaces of petiolar and postpetiolar nodes and side of postpeciolar node longitudinally rugulose. Dorsal surface of postpetiolar node rather smooth and shining. Longitudinal rugulae at the base of the gaster less than 0.10 mm in length.

Body rather uniformly dark reddish brown, with even lighter, appendages. Eyes black. Mandibular teeth, region around the ocelli, epinotal spines and (certain regions of the thorax, when viewed in some lights) blackish. Mayr described the female as black-brown, mandibles and clypeus rust-red, antennae and legs more yellowish red, partly with a touch of brownish.

Male
Length 2.9-3.1 mm. Eye large, oval, approximately 0.2-0.25 mm in, its greatest diameter. Ocelli placed approximately 0.10 mm posterior to an imaginary transverse line connecting the posterior borders of the eyes, Frontal area distinct, longer than broad. Scape short, approximately 0.2-0.25 mm long, as long as the combined lengths of the first 2.5-3.5 funicular segments. Thorax measured similar 'to that of' the worker, 1.25-1.3 mm long, widest at the base of the anterior wings, where it measures 0.65-0.7 mm. Mayrian furrows present but not strongly developed. Parapsidal sutures also present but only clearly seen in some lights. In profile, base of the epinotum distinctly concave to almost straight, approximately twice as long as the epinotal declivity and meeting the declivity in a distinct angle. Petiolar node, in profile, distinctly angular. Postpetiole, from above, approximately as broad as long.

Mesopleuron, much of epinotum, especially the base and declivity, dorsal surfaces of petiolar and postpetiolar nodes, and gaster, smooth and shining; most of head and thorax rather delicately sculptured and subopaque, especially in some lights.

Pilosity moderately abundant, of variable length, largely inclined or suberect.

Body blackish to black, with lighter mandibles, antennae and legs. Wings pale, with light brown veins and stigma.

Males from other localities differ from the above described paratypes as follows: Body length 3-3.5 mm; head 1.2-1.3 times as long as broad; frontal area present but not always very distinct; antennal scape (exclusive of the pedicel) 0.2-0.3 mm in length and as long as the combined lengths of the first 2.5-4 funicular segments; mandibles with 2-3 teeth; thoracic length 1.15-1.4 mm; base of epinotum approximately 1.5-2 times as long as the declivity; Mayrian furrows present but varying from weak, scarcely distinct to rather well developed; postpetiole from approximately as broad as long to broader than long; anterior wing venation of some individuals highly aberrant, the discoidal cell lacking in one or both wings, and also the equivalent of an extra (second) cubital cell present in one or both wings.

Type Material
Described from a holotype and 53 paratype workers and 14 paratype males, all of which have been deposited in the U. S. National Museum under No. 62394. Rustlers Park, Chiricahua Mountains, Arizona.

Etymology
Patronym. Bolton, discovering the name occidentalis was invalid, assigned this name in homage to Roy Snelling.

References based on Global Ant Biodiversity Informatics

 * Allred D. M. 1982. Ants of Utah. The Great Basin Naturalist 42: 415-511.
 * Allred, D.M. 1982. The ants of Utah. Great Basin Naturalist 42:415-511.
 * Cover S. P., and R. A. Johnson. 20011. Checklist of Arizona Ants. Downloaded on January 7th at http://www.asu.edu/clas/sirgtools/AZants-2011%20updatev2.pdf
 * Gregg, R.T. 1963. The Ants of Colorado.
 * Johnson R. Personnal Database. Accessed on February 5th 2014 at http://www.asu.edu/clas/sirgtools/resources.htm
 * Johnson, R.A. and P.S. Ward. 2002. Biogeography and endemism of ants (Hymenoptera: Formicidae) in Baja California, Mexico: a first overview. Journal of Biogeography 29:10091026/
 * Mackay W. P., and E. E. Mackay. 2002. The ants of New Mexico (Hymenoptera: Formicidae). Lewiston, New York: Edwin Mellen Press, 400 pp.
 * Mackay, W., D. Lowrie, A. Fisher, E. Mackay, F. Barnes and D. Lowrie. 1988. The ants of Los Alamos County, New Mexico (Hymenoptera: Formicidae). pages 79-131 in J.C. Trager, editor, Advances in Myrmecololgy.
 * Smith M. R. 1957. Revision of the genus Stenamma Westwood in America north of Mexico (Hymenoptera, Formicidae). American Midland Naturalist 57: 133-174.
 * Snelling R. R. 1973. Studies on California ants. 7. The genus Stenamma (Hymenoptera: Formicidae). Contributions in Science (Los Angeles) 245: 1-38.
 * Vásquez-Bolaños M. 2011. Lista de especies de hormigas (Hymenoptera: Formicidae) para México. Dugesiana 18: 95-133
 * Wetterer, J. K.; Ward, P. S.; Wetterer, A. L.; Longino, J. T.; Trager, J. C.; Miller, S. E. 2000. Ants (Hymenoptera: Formicidae) of Santa Cruz Island, California. Bulletin of the Southern California Academy of Sciences 99:25-31.
 * Wetterer, J.K., P.S. Ward, A.L. Wetterer, J.T. Longino, J.C. Trager and S.E. Miller. 2000. Ants (Hymenoptera:Formicidae) of Santa Cruz Island, California. Bulletin of the Southern California Academy of Science 99(1):25-31.