Pheidole rugulosa Gregg

Wilson, E. O., 2003, Pheidole in the New World. A dominant, hyperdiverse ant genus., Cambridge, MA: Harvard University Press : 595

Pheidole rugulosa Gregg

Pheidole rugulosa Gregg 1959: 26.

Types Mus. Comp. Zool. Harvard.

Etymology L rugulosa , a small amount of wrinkling, evidently referring to the occipital rugulation.

Diagnosis A member of the " pilifera complex" of the larger pilifera group; for a characterization of the complex, see under pilifera .

P. rugulosa is distinguished within the complex by the following combination of traits.

Major: rugulae on occiput seen in full-face view limited to a narrow strip; longitudinal carinulae originating on the frontal triangle travel all the way to meet the occipital rugulae, but other cephalic carinulae do not reach beyond the midpoint of the head capsule; anterior strip of the pronotum transversely carinulate; mesonotal convexity very low; postpetiole seen from above laterally angulate. Minor: exceptionally large, forward-placed eyes; mesonotal convexity present in dorsal-oblique view; propodeal spines well developed.

Throughout much of southern New Mexico and Arizona, P. rugulosa occurs with P. soritis , with which it is easily confused.

P. rugulosa is most easily distinguished from that species by the major's well-developed humeral angles, which are inconspicuous and rounded in soritis , and the large shiny areas on the posterior dorsal surface of the head, which is variably sculptured in soritis .

Measurements (mm) Paratype major: HW 1.04, HL 1.12, SL 0.54, EL 0.22, PW 0.56.

Paratype minor: HW 0.52, HL 0.52, SL 0.42, EL 0.14, PW 0.44.

Color Major: reddish to medium brown, gaster often somewhat darker. Minor: medium to dark brown, even blackish.

Range Texas, New Mexico, Arizona.

biology Stefan Cover (unpublished collection notes) found numerous colonies of rugulosa in the deserts of southern Arizona and southwestern New Mexico at 1300-1700 m, in xeric habitats ranging from grazed grassland desert to rabbitbrush-mesquite desert, mesquite-acacia dominated wash, and riverbank desert scrub. The ants usually nest in the open soil, with the entrances surrounded by either crescentic or full craters; the entrance of one nest was in a grass clump. Similar nest site preferences are reported from western Texas by Moody and Francke (1982). According to Cover, colonies may consist of several hundred individuals or more, and, unusually for Pheidole , are at least sometimes polygynous. Seeds are occasionally found in the nests.

figure Upper: paratype, major. Lower: paratype, minor. ARIZONA: Tucson. Scale bars = 1 mm.