Myrmecocystus snellingi

Only known to nest in areas with fine drifting sands.

Identification
Worker.—Scape, malar area and propodeum with abundant erect hairs; erect pronotal hairs abundant; pubescence of second tergum sparse to scattered. Female and Male.—Forewing without erect hairs on membrane. (Snelling 1982)

Distribution
Only known from Nevada.

This taxon was described from the United States.

Biology
Snelling (1982) - The Wheelers and I were able to study this species briefly one day at a station six miles north of Nixon. This is an area of fine, drift-prone sand along the east side of Pyramid Lake. There was a sparse cover of Salsola pestifer and Dalea polyadenia. In one sector the annual, Abronia turbinata, was present and in bloom.

Two nests were situated in unstable sand with sparsely distributed Salsola and scattered Dalea plants. The third was in stabilized sand with denser cover, including Abronia. The only ant species common there was Pogonomyrmex californicus (Buckley). Messor lariversi and Dorymyrmex insanus were also present but uncommon.

Workers of Myrmecocystus arenarius (=snellingi) were found foraging up to midmorning. Some were carrying miscellaneous fragments of other arthropods. A number of workers were also seen at nectaries of the Salsola. A single semireplete worker was recovered from one nest, but the unstable condition of the sand rendered deep excavation impractical.

Nomenclature

 * arenarius. Myrmecocystus (Eremnocystus) arenarius Snelling, R.R. 1982b: 71, figs. 1-6, 13, 15, 19, 21, 23 (w.q.m.) U.S.A. [Junior primary homonym of arenaria Finzi, 1940: 164, above.] Replacement name: snellingi Bolton, 1995b: 275.
 *  snellingi. Myrmecocystus snellingi Bolton, 1995b: 275. Replacement name for arenarius Snelling, R.R. 1982b: 71. [Junior primary homonym of arenaria Finzi, 1940: 164.]

Worker
Measurements: HL 0.65-1.02 (0.95); HW 0.58-0.90 (0.89); SL 0.66-1.07 (0.96); WL 0.83-1.40 (1.22); PW 0.42-0.63 (0.59).

Head: Longer than broad in all sizes, CI 105-119 (105); in full face view, malar margins nearly straight and convergent toward mandibles in smallest specimens, slightly convex in largest; occiput nearly flat in smallest workers, weakly convex in largest, sides broadly rounded; as long as, to a little shorter than, scape, SI 100-110 (101). Eye small to moderately large, EL 1.00-1.40 (1.31) X first flagellomere; OMD 1.17-1.54 (1.29) X EL. Mandible with seven teeth.

Thorax: Moderately robust, PW 0.43-0.52 (0.48) X WL. Mesonotum, in profile, nearly straight in smallest workers, broadly rounded into a sloping posterior face in largest specimens. Basal face of propodeum, in profile, short and broadly rounded into posterior face in small specimens, distinct, long, and abruptly rounded into posterior face in largest specimens.

Petiole: In profile, compressed and narrowly cuneate; spiracles distinctly projecting in larger specimens; crest broadly concave, in posterior view, in large specimens, flat or weakly notched in small individuals.

Vestiture: Pubescence scattered on head; long and dense, but not concealing surface, on thorax and first gastric tergum. Second tergum with scattered pubescence, usually more conspicuous (especially in larger individuals) along base, midline and at sides of disc. Erect hairs numerous on head; malar area with 5- 11 suberect hairs; scape with sparse erect hairs and numerous shorter, decumbent to subdecumbent hairs; all surfaces of femora and tibiae with numerous erect and suberect hairs. Promesonotum with numerous erect hairs, the longest more than 0.5 X MOD; metanotum usually without erect hairs; dorsum of propodeum with 6 or more fine, short erect hairs. Petiolar scale with erect hairs on sides and crest. Terga with numerous discal hairs, becoming a little longer on succeeding segments.

Integument: Clypeus shiny, with scattered fine and coarse piligerous punctures; remainder of head subpolished, very weakly shagreened, with scattered piligerous punctures, frontal lobes virtually impunctate. Thoracic dorsum shiny, lightly shagreened. Gaster shiny, feebly shagreened.

Color: Medium to dark brown, appendages a little lighter; mandibles and apical part of clypeus yellowish brown, mandibular teeth dark red.

Queen
Measurements (mm): HL 1.36-1.38; HW 1.36-1.41; SL .36-.38; WL 2.51-2.78; PW 1.71-1.87.

Head: As broad as, or a little broader than, long, CI 95-100; in full face view, malar margin nearly straight or very weakly convex; distinctly longer than scape, SI 85-95. Eye small, EL 1.00-1.20 X first flagellomere; OMD 1.00-1.25 X EL. Mandible with seven teeth. Lateral ocelli slightly smaller than anterior ocellus, IOD 2.62-3.28 X OD; OOD 3.50-4.14. X OD. Fifth segment of maxillary palp broad at base, broadest near middle, distinctly narrowed distad; fourth segment narrowest at base, gradually broadened distad.

Thorax: Robust, PW 0.62-0.73 X WL. Posterior half of mesoscutum flattened; scutellum sloping and flat or very gently convex in profile. Basal portion of propodeum, in profile, sloping and abruptly rounded onto declivous face.

Petiole: Strongly compressed in profile, summit thin; in frontal view, sides a little convergent above; median emargination broad, deep, angulate; from above about 3 X wider than long.

Vestiture: Pubescence appressed, very scattered on head, most abundant (but still sparse) on lower malar area; appressed to subdecumbent on mesoscutum, scattered; longer, sparse, prostrate to suberect on sides of thorax, densest on pronotum and propodeum; appressed and scattered on tergal discs, becoming a little more abundant toward sides and apical margins.

Scape with pubescence subdecumbent to suberect and with scattered fine, suberect hairs; femora and tibiae with abundant appressed to subdecumbent pubescence and numerous subdecumbent to erect hairs on all surfaces, least abundant on dorsal (extensor) femoral surfaces. Malar area, in frontal view, with 6-10 subdecumbent hairs; remaining frontal and dorsal head surface with rather sparse, short subdecumbent to erect hairs, longest hairs on occiput more than 0.5 X MOD. Scutum with sparse suberect to erect hairs, mainly peripherally, longest no more than 0.5 X MOD; scutellum with scattered suberect to erect hairs, longest more than MOD; pleura with scattered suberect to erect hairs, longest about 0.5 X MOD; propodeum with sparse erect hairs across base and at sides of declivity. Petiolar scale with a few short, erect hairs on sides and across summit. All terga with sparse, suberect to erect hairs, becoming longer and coarser caudad, longest on disc of second segment no more than 0.5 X MOD.

Membrane of forewing without obvious erect hairs at 45X; forewing without fringe hairs and hindwing with a very few on basal half of posterior margin.

Integument: Shiny and very weakly, or not at all, shagreened on most areas, including gastric terga; metapleuron and propodeum conspicuously duller.

Head generally with scattered minute punctures; clypeus with a few fine punctures. Mesoscutum with scattered fine punctures, middle of disc nearly impunctate; minute punctures even more scattered. Scutellum with sparse, fine setigerous punctures. Anepisternum for the most part with sparse to scattered fine and minute punctures; katepisternum similar but with posterior and posterodorsal zones of dense punctures; metapleuron and propodeum densely and finely punctate. Tergal discs with sparse to scattered minute to ultraminute punctures.

Color: Medium brown, sides and propodeum darker; appendages light brown. Wings hyaline, veins and stigma yellowish brown.

Male
Measurements (mm): HL 0.60-0.64 (0.64); HW 0.54-0.60 (0.60); SL 0.58-0.64 (0.64); WL 1.15-1.33 (1.33); PW 0.76-0.88 (0.76).

Head: Slightly to distinctly longer than broad, CI 104-117 (106), as long as, or longer than, scape, SI 94-100. In frontal view, margins distinctly convergent toward mandibular bases; occiput broadly convex, lateral angles broadly rounded. Eye large, OMD 0.47-0.65 (0.53) X EL; lateral ocelli slightly larger than anterior, IOD 3.20-4.00 (3.75) X OD; OOD 2.75-3.25 (3.25) X OD. Mandible with distinct preapical cleft and one or two small teeth on cutting margin.

Thorax: Stout, PW 0.57-0.70 (0.57) X WL. Mesoscutum broad, vertical in front, posterior half fiat or weakly concave; scutellum, in profile, with fiat dorsal surface and abruptly sloping posterior face. Basal face of propodeum, in profile, narrow, convex and abruptly rounded into posterior face.

Petiole: Cuneate in profile, posterior face weakly convex, summit narrowly rounded; posterior view, crest straight or broadly and very shallowly concave.

Pilosity: Pubescence very fine, short, very scattered, most conspicuous on metapleuron and side of propodeum.

Scape with numerous very fine and short subdecumbent to suberect hairs; femora and tibiae with longer, coarser, sparse suberect hairs on all surfaces. Head and thorax with sparse to scattered subdecumbent to erect hairs, longest occipital hairs about 0.5 X MOD. Gastric terga with sparse, subdecumbent to erect hairs, longest on disc of second segment no more than 0.5 X MOD. Wings as in female. Integument: Shiny and, at most, very weakly shagreened on most surfaces of head, thorax and gaster; metapleuron and basal face of propodeum moderately shiny, closely, though weakly, punctulate.

Color: Medium brown, occiput and thoracic dorsum a little darker, gaster a little paler. Appendages light brown. Wings hyaline, veins and stigma very pale brownish.

Etymology
Latin, arenarius (pertaining to, or of, sand) because of the apparent preference of this ant for habitats of fine dune sand.