Pheidole xerophila Wheeler

Pheidole xerophila Wheeler

Pheidole xerophila Wheeler 1908h: 446. Syn.: Pheidole xerophila subsp. tucsonica Wheeler 1908h: 448, synonymy by Creighton and Gregg 1955: 42.

Types Mus. Comp. Zool. Harvard.

etymology Gr xerophila, aridity lover.

Diagnosis A small, large-eyed member of the pilifera group, close to gilvescens and distinguished as follows. Major: parts variously reddish yellow to light reddish brown; postpetiolar node transversely conulate, nearly 2X broader than the petiolar node; sides of pronotum mostly free of carinulae, and smooth. With gilvescens, also similar to bajaensis and yaqui, both differing in the major by the flattened profile of the dorsal posterior half of the head in side view, and by the head tapering conspicuously from the midline to the occiput in side view. The form "subspecies tucsonica" is here treated as a geographic variant with a transversely rugulose pronotal dorsum (as figured above), which as Creighton and Gregg (1955) pointed out, is found from central Texas westward through southern New Mexico and Arizona to the mountains of southern California and southward into Sonora as far as Guayamas. "Typical" xerophila, with a mostly smooth pronotal dorsum (see figure above) ranges from the Big Bend of Texas into southwestern New Mexico. Because intermediates in the pronotal sculpturing occur in central Mexico, Creighton and Gregg (1955) treated tucsonica as a subspecies of xerophila. Snelling and George (1979), although confirming the intergradation, raised tucsonica to species level, and this step was followed by G. C. and J. Wheeler (1986g). On the evidence I have kept tucsonica as part of xerophila, but this is not a firm conclusion; Snelling and George may be right in considering the intermediates as no more than rare hybrids.

Measurements (mm) Syntype major: HW 1.28, HL 1.42, SL 0.62, EL 0.20, PW 0.60. Syntype minor: HW 0.56, HL 0.60, SL 0.52, EL 0.20, PW 0.36.

color Major: head and legs medium reddish yellow; mesosoma and rest of appendages dark reddish yellow, waist and gaster light reddish brown.

Minor: body medium yellowish brown; appendages light yellowish brown.

range Central Texas to southern California and Sonora, Mexico; see further account in Diagnosis above.

biology Snelling and George (1979) report that in southern California xerophila (" tucsonica ") occurs at 150-1500 m, in creosote bush scrub and Joshua-tree and oak-juniper woodland. The colonies contain 30-40 majors and 300-400 minors and build small, low craters in the sand, often surrounded by seed chaff. Caches of seed are present. Similarly, G. C. and J. Wheeler (1986g) found the species ("subspecies tucsonica") locally abundant in southernmost Nevada, where it forms crater nests in fine sand, sometimes ringed by seed chaff; the nest chambers also contained insect fragments. In western Texas, Moody and Francke (1982), found the species relatively common between 600 and 1800 m, nesting mostly in open soil but occasionally beneath stones. In the Chihuahuan and Sonoran deserts of southern Arizona and New Mexico Stefan Cover (personal communication) found it one of the commonest Pheidole, occurring with hyatti, rugulosa, and soritis. It harvests seeds along trunk trails, with the large majors often accompanying the minors.

Figure Upper: syntype, major. Lower: syntype, minor. TEXAS: Ft. Davis, Jeff Davis Co. Additional major promesonotum: syntype of synonymous P. xerophila subsp. tucsonica Wheeler (Tucson, Arizona). Scale bars = 1 mm.