Pheidole militicida Wheeler

Wilson, E. O., 2003, Pheidole in the New World. A dominant, hyperdiverse ant genus., Cambridge, MA: Harvard University Press : 586

Pheidole militicida Wheeler

Pheidole militicida Wheeler 1915b: 398.

Types Mus. Comp. Zool. Harvard.

etymology L militicida , soldier killer, based on Wheeler's mistaken belief that colonies of this species periodically execute their own majors.

Diagnosis A giant species of the pilifera group distinguished in addition as follows.

Major: reddish yellow; petiolar node in side view tapering to a blunt point, its apex bearing a transverse carina; the postpetiolar node from above angulate, its crest also bearing a transverse carina; a small, angular subpostpetiolar process present; the posterior half of the head and almost all the rest of the body smooth and shiny; pilosity erect, relatively short, and very dense. Minor: eye very large, head quadrate in full-face view; humerus lobose in dorsal-oblique view; postpetiolar node depressed; almost all of the body smooth and shiny.

Measurements (mm) Syntype major: HW 2.66, HL 2.50, SL 0.96, EL 0.32, PW 1.20. Syntype minor: HW 0.84, HL 0.92, SL 0.74, EL 0.26,. PW 0.52.

color Major: concolorous reddish yellow. Minor: body dark reddish brown, appendages brownish yellow.

range Southern Arizona, New Mexico, extreme western Texas.

Biology P. militicida builds crater nests, often surrounded by piles of seed chaff in the soil of deserts. Stefan Cover and Gary D. Alpert (unpublished collection data) found nests at 1300-1500 m; winged queens and males are present in at least the first half of July, in separate collections by G. D. Alpert, W. S. Creighton, and S. P. Cover. The species is also a major seed harvester in xeric habitats. Holldobler and Moglich (1980) have described trunk trails laid out by minors along which thousands of ants travel to the areas where seeds are then harvested and brought back to the nest. The system resembles that of the famous desert harvester ants of the genera Messor and Pogonomyrmex . The trunk trails start as chemical recruitment trails and are stabilized by more enduring chemical orientation cues and visual markers. And like Messor , the workers shift the direction of the foraging pathway or establish a new route when the seed supplies in the target foraging area diminish. Because W. M. Mann and W. M. Wheeler found majors in the nests near Benson, Arizona, in the seed-bearing season of August and remains of majors on the chaff piles in November, Wheeler (1915b) speculated that majors are produced in the colony prior to the harvesting season and killed afterward -hence the name he gave the species. This hypothesis was persuasively discarded but not entirely disproved by Creighton and Gregg (1955). A careful study of the life cycle and division of labor in this unusual species will prove rewarding. The disproportionately huge major suggests that it may also be a storage caste. The majors are also the focus of a myrmecological mystery story.

Figure Upper: syntype, major. Lower: syntype, minor. ARIZONA: Hereford, Cochise Co. Scale bars = 1 mm.