Myrmecocystus colei

A daytime foraging Myrmecocystus species that nests in compacted clayey soil.

Identification
A member of the subgenus Eremnocystus.

Key to Myrmecocystus subgenus Eremnocystus species.

This species does not appear to be very closely related to any of the other species of Eremnocystus. In the abundant appressed pubescence it is most like Myrmecocystus hammettensis, but workers of that species possess numerous fully erect hairs on the scapes and cheeks. The female Myrmecocystus colei has the mesoscutum densely and uniformly covered with fine punctures while that of hammettensis has the scutum sparsely and coarsely punctate. In colei females the penultimate segment of the maxillary palp is broad basally and tapers to a narrow apex; it is nearly parallel-sided in hammettensis. (Snelling 1976)

Distribution
Known from coastal and intermediate valleys of southern California.

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



Biology
This ant is known to occur in the coastal sagebrush phytocenose, along stream drainages, up to areas where this habitat grades into the Oak-Juniper-Joshua tree association. Nests are constructed in compacted clayey soil, usually overlain with gravel or coarse sand. Foraging activities appear to be fully diurnal, with workers active out of the nest at midday. The workers are assiduous scavenger-predators and also collect large quantities of nectar from flowers. (Snelling 1976)

Previous records for this ant have been from coastal valley stations. New Mojave Desert samples were a little less pilose than those from coastal stations. Our samples were from the bed of a sandy wash dominated by Salsola iberica in rolling grassland which had been Joshua Tree Woodland until cleared. (Snelling (1982)

Nomenclature

 *  colei. Myrmecocystus (Eremnocystus) colei Snelling, R.R. 1976: 94, figs. 203-211, 255-258 (w.q.m.) U.S.A.

Worker
Scape with a few scattered erect hairs; dorsum of propodeum with erect hairs; petiolar scale erect but not compressed; erect pronotal hairs apically acuminate; hind femur with numerous erect hairs on inner face. Female: Mesoscutum finely, densely, uniformly punctate; occiput shiny, with scattered fine punctures; mid and hind femora without conspicuous erect hairs except on ventral margin. Male: Forewing without marginal fringe beyond stigma; hind-wing without marginal fringe; petiole not, or scarcely, emarginate.

Measurements. HL 0.76-1.26 (1.06); HW 0.60-1.13 (0.93); SL 0.90-1.33 (1.20); WL 1.10-1.66 (1.46); PW 0.46-0.73 (0.66).

Head: In all sizes from distinctly to slightly longer than wide, CI 77-93 (87); in full face view, sides straight (barely convex in largest workers), slightly convergent toward mandibular insertions; occiput flat with comers rounded, but distinct; shorter than scape, SI 105-121 (112). Eye small, slightly longer than first flagellomere; OMD 1.25-1.75 (l.45) X EL. Mandible septendentate, occasionally with intercalary denticle between basal and penultimate basal teeth.

Thorax: Moderately robust, PW 0.39-0.48 (0.47) x WL. Mesonotum, in profile, evenly convex from front to back except in largest workers where it is abruptly declivitous behind. Basal face of propodeum distinct, sharply rounded into the longer posterior face.

Petiole: Scale erect, in profile about twice higher than thick; posterior face straight, anterior rather abruptly narrowed in upper third; crest narrow in frontal view, flat in smallest workers, slightly concave in largest; from above, about twice wider than long.

Vestiture: Pubescence sparse on malar area and clypeus; sparse to abundant on frontal lobes and abundant on occiput, but not obscuring surface; abundant and long on thoracic dorsum and pleura, but sparser and finer on propleura, loosely appressed to subappressed; abundant, but not concealing integument, on first three terga (sparser on third tergum of some minors), sparse on remaining segments.

Scape, inner face of fore femur, outer faces of middle and hind tibiae with fine suberect to erect hairs; malar area, in frontal view, with a few reclinate to suberect hairs; clypeal disc, front of head and occiput with numerous erect hairs, those of occiput about half as long as minimum eye diameter. Pronotum and mesonotum with conspicuous fully erect hairs, usually fewer than 15 on each segment, shorter than those of occiput; posterior half of propodeal dorsum with at least 10 fully erect short hairs. All terga with numerous erect, short hairs, progressively longer caudad.

Integument: Clypeus shiny, with scattered fine piligerous punctures; remainder of head moderately shiny, lightly shagreened. Thorax lightly shagreened, moderately shiny, more so on sides. Gaster moderately shiny, distinctly though finely shagreened.

Color: Integument light to dark brownish, appendages lighter; mandibles, clypeus and lower portions of malar area yellowish.

Queen
Measurements. HL 1.40-1.46; HW 1.361.43; SL 1.36-1.43; EL 0.36-0.40; OMD 0.53-0.56; WL 2.8-3.1; PW 1.8-2.0.

Head: As broad as, or broader than, long; CI 100-104; in full face view with sides straight, not convergent toward mandibular insertions; occiput flat or slightly convex, comers narrowly rounded; as long as, or longer than, scape, SI 96-100. Eye a little longer than first flagellomere; OMD 1.33-1.42 X EL. Ocelli subequal; IOD 3.0-3.3 x OD; OOD 2.6-3.0 x OD. Mandible septendentate. Penultimate maxillary palpal segment elongate-triangular, greatly narrowed apically; segment three narrowed basally and apically, otherwise uniform in breadth; segment four uniformly broadened from base to apex.

Thorax: Robust, PW 0.58-0.67 x WL. Mesoscutum low in profile, somewhat flattened and gently curved into profile of scutellum; scutellum gently convex, a little more strongly sloping behind; propodeum with distinct transverse basal horizontal face and precipitous posterior face, their juncture sharply rounded.

Petiole: In profile, compressed above, crest sharp; in frontal view, sides convergent toward crest, crest broadly and deeply angularly excised; from above about three times wider than thick.

Vestiture: Pubescence sparse on clypeus; abundant elsewhere on head, thorax and gaster; long, subappressed to reclinate on occiput, pleura and propodeum.

Scape with abundant short, reclinate hairs; anterior femur without erect hairs on inner face; middle and hind tibiae with abundant suberect hairs. Malar area, in frontal view, with 6-8 long, erect yellowish hairs; clypeus with numerous erect yellowish hairs of highly variable length; frons with numerous erect yellowish hairs; occipital hairs much longer, some more than 0.5 x MOD; scutum with numerous widely spaced erect yellowish hairs, less than 0.5 x MOD; scutellum with longer erect hairs, some equal to MOD; metanotum with a few long erect hairs; propodeum with a few short erect hairs on dorsal face; pleura with scattered long erect yellowish hairs, more numerous below; petiolar scale with numerous fine whitish hairs; first three terga with short, erect yellowish hairs, becoming more abundant from first to third; subsequent terga with hairs longer, sparser than on third. Wing membranes with fine whitish hairs, costal margin of forewing, to stigma, with sparse fringe.

Integument: Clypeus polished, with coarse setigerous punctures; remainder of face shiny (but somewhat obscured by pubescence), with dense fine piligerous punctures and scattered coarse, setigerous punctures; malar area with abundant coarse, elongate punctures; occiput duller, closely shagreened, and with fine, close punctures. Mesoscutum shiny, uniformly finely, densely punctate; scutellum shiny, evenly, more sparsely punctate; pleura duller, closely shagreened and with abundant fine and sparser, coarser punctures; propodeum dull, densely shagreened, with dense fine, obscure punctures; terga shiny, lightly shagreened and with abundant fine punctures.



Color: Brownish, mesosoma darker; mandibles, sides of clypeus and lower half (or less) of malar area, yellowish.

Male
Measurements. HL 0.63-0.73; HW 0.60-0.66; EL 0.26; SL 0.66-0.76; OMD 0.16-0.20; WL 1.30-1.66; PW 0.80-0.90.

Head: Margins nearly parallel below eyes, not notably convergent toward mandibular bases; head a little longer than broad, CI 90-95 (95), a little shorter than scape, SI 105-110 (105); occiput gently convex, with distinct lateral angles. Eye large, OMD 0.63-0.75 (0.63) x EL; ocelli subequal; IOD 3 x OD; OOD 1.5-2.0 x OD. Mandibles with preapical cleft and low preapical tooth, margin edentate or with one or two minute denticles.

Thorax: Stout, PW 0.53-0.57 x WL. Mesoscutum broad, anterior face vertical, anterior half strongly convex, posterior half more flattened; scutellum nearly vertical behind; propodeum with transverse, horizontal basal area and vertical posterior face, their juncture angulate.

Petiole: In profile, cuneate; crest, seen from front, nearly flat or with obscure median emargination; in dorsal view, about twice wider than long.

Vestiture: Appressed white pubescence sparse on head; more abundant and somewhat yellowish on thoracic dorsum; more abundant, whitish, on pleura and propodeum; denser on first three terga.

Erect hairs sparse, conspicuously longer on occiput than elsewhere on head, those of scutellum longer than elsewhere on thorax; disc of first tergum with a few erect yellowish hairs; remaining terga with a more numerous, conspicuously longer yellowish hairs. Wing membrane, with numerous very short whitish hairs; fringe hairs present along costal margin of forewing to stigma.

Type Material
Holotype worker, allotype male, 12 queens, 73 males and 29 woker paratypes: San Gabriel R., 500', Irwindale, Los Angeles Co., CALIF., 22 Feb. 1963 (R. H. Crandall and R. R. Snelling) in. Additional paratypes: 8 males, 27 Symbol, type locality, 24 Feb. 1963 (R. R. Snelling; LACM). Three paratypes to each of the following collections:, GCW, , , and.