Pheidole rhea Wheeler

Wilson, E. O., 2003, Pheidole in the New World. A dominant, hyperdiverse ant genus., Cambridge, MA: Harvard University Press : 594

Pheidole rhea Wheeler

Pheidole rhea Wheeler 1908h: 452.

TYPES Unique holotype queen: Department of Entomology Collection, Cornell University, Ithaca, New York.

etymology NL rhea , a South American genus of ostrichlike birds, allusion unknown.

Diagnosis A giant species, reddish to dark brown, tentatively placed in the pilifera group because of the bidentate hypostoma and presence ofa supermajor, but with overall appearance similar to some species of the fallax group. Trimorphic, with major, supermajor, and minor castes, as illustrated. Also distinguished as follows.

Major: head completely covered everywhere except on frontal triangle by dense longitudinal carinulae; promesonotum smoothly convex in both side and dorsal-oblique views; propodeal spines very long; posterior face of propodeum descends vertically; postpetiole diamond-shaped from above.

Supermajor: propodeum descends vertically; postpetiole diamond-shaped from above; cephalic sculpturing as in major, except that the carinulae of the dorsal face behind the level of the eye curve inward toward the cephalic midline. Minor: very long propodeal spines, as illustrated.

Measurements (mm) All castes measured are from Stratton, Santa Catalina Mts., Arizona. Supermajor: HW 3.86, HL 4.04, SL 1.68, EL 0.38, PW 1.38. Major: HW 2.52, HL 2.76, SL 1.40, EL 0.26, PW 1.04. Minor: HW 0.86, HL 0.96, SL 1.06, EL 0.16, PW 0.58.

color Major and minor: body light reddish brown, except for the gaster, which is a slightly contrasting dark reddish brown.

Range Southern Arizona south into Mexico.

Biology The species is found on plateaus and among foothills at the bases of mountains across a wide elevational range, from 1100 to 2100 m, with an apparent preference for the lower end (Creighton 1950a: 168). According to Stefan Cover (personal communication), it "forms enormous colonies surmounted by sloppy craters or under rocks, chiefly on open, rocky slopes. Seeds are harvested in large quantities, but the ants are active predators as well. Mature colonies have well-developed trunk-trail systems. Minors and medias forage, but large majors and supermajors are seldom seen outside the nests. The ants are aggressive, and all size classes actively defend the nest."

figure Upper: major, with partial view of supermajor head at far right. Lower: minor. ARIZONA: Stratton, Santa Catalina Mts., northeast of Tucson. (Type locality: Nogales, Arizona.) Scale bars = 1 mm.