Stenamma dyscheres

A rarely collected species that is poorly known. Specimens have been sifted from leaf litter in a mixed coniferous forest and from pine duff.

Identification
Worker with 2-4 facets in EL, OMD 2.0-4.0 x EL; median lobe of clypeus notched in frontal view; first tergite largely polished, basal one fourth or less with fine longitudinal striae; first sternite with sparse longitudinal striae which are coarse and conspicuous, or with numerous very fine striations, inters paces usually smooth and shiny, but fine punctulae may be present, particularly on sides.

Workers are medium ferruginous, legs and antennae yellowish, to brownish ferruginous with mandibles, lower third of head and appendages paler.

There are two forms of this species, which may in fact be two true species. More material is needed to resolve this issue. The type series consists of;similar workers in which the integument is moderately to strongly shiny on the thorax and petiolar nodes. The thoracic rugulae are coarse and well defined. The first gastric sternite has a number of widely spaced, rather coarse longitudinal striae and the corresponding tergite has numerous coarse striae basally, these about 0.2 mm long. The nodes of the petiole and postpetiole are conspicuously longitudinally rugulose.

Most of the remaining specimens are, on the average, smaller, with thoracic rugulae quite fine and the interspaces closely punctulate, hence only slightly shiny. The first gastric sternite is very finely and closely longitudinally striate with a few punctulae between striae, especially toward the sides. The base of the first tergite is closely and finely striate, the striae 0.13 mm long, or less. These closely punctulate specimens also usually have short, triangular propodeal spines, but the series from the Tehachapi Mountains has the spines about as long as in the types.

Among the species with sculptured gastric segments Stenamma dyscheres most closely resembles Stenamma punctatoventre and Stenamma californicum; Stenamma punctatoventre may be immediately separated by the shape of the median clypeal lobe, which is produced and appears truncate in frontal view. In Stenamma californicum the rugulae on the sides of the thorax are ·much reduced and very obscure because of the fine, dense punctulation; this is especially evident on the mesopleura which usually is without rugulae and on the propodeal sides which may have a few rugulae below the spiracle but none above it. In this species, too, the basal one-fourth or more of the first tergite is finely punctulate and without evident striations except the usual ones at the basal articulation. Finally, the sculpture of the first sternite consists of fine, dense punctulation. Those specimens of Stenamma dyscheres which possess dense punctulae on the sides of the thorax retain the coarse, conspicuous rugulae on the mesopleura and propodeal sides and the base of the first tergite is conspicuously striate, the articular striae interspersed with longer, finer supplementary striae. The sternite is striate, the striae coarse or fine and punctulae may be present laterally between striae.

Snelling 1973

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

Range
USA. California. Low to moderate elevations in the Sierra Nevada foothills south to Tejon Pass area of the Tehachapi Mountains; in the north, westward into the upper Sacramento Valley.

Nomenclature

 *  dyscheres. Stenamma dyscheres Snelling, R.R. 1973c: 21, figs. 28, 29, 34, 35 (w.q.m.) U.S.A.

Type Material
Holotype worker, allotype male and 9 workers, 21 male paratypes: Bull Flat, 3600', T5N, R.18E, Tuolumne Co., CALIF., 6 Sept. 1967 (G. C. and J. N. Wheeler; #187, CALIF). Holotype, allotype and 2 workers, 7 male paratypes in LACM; 2 workers, 4 male paratypes in GCW; 1 worker, 2 male para types in each: AMNH, MCZ, USNM, ACC, WSC.

Type Locality Information
Bull Flat, 3600', T5N, R.18E, Tuolumne Co., CALIF., 6 Sept. 1967 (G. C. and J. N. Wheeler; #187, CALIF).

Etymology
Descriptive. Dyscheres, Gr., vexatious or difficult; in allusion to the extreme variability of this species and the difficulty in characterizing it.

Additional References

 * Snelling, R. R. 1973. Studies on California ants. 7. The genus Stenamma (Hymenoptera: Formicidae). Contributions in Science (Los Angeles). 245:1-38.