types Mus. Comp. Zool. Harvard.
Etymology L Ceres, the pre-Roman goddess of agriculture, evidently in reference to the seed-harvesting practiced by the species.
diagnosis A member of the " bicarinata HNS complex" of the larger pilifera HNS group, comprising agricola HNS , aurea HNS , barbata HNS , bicarinata HNS , centeotl HNS , cerebrosior HNS , ceres HNS , defecta HNS , gilvescens HNS , macclendoni HNS , macrops HNS , marcidula HNS , paiute HNS , pinealis HNS , psammophila HNS , vinelandica HNS , xerophila HNS , yaqui HNS , and yucatana HNS , which complex is characterized by the large to very large, forward-set eyes, especially in the minor; and in the major, the occipital lobes lacking any sculpturing (except in aurea HNS ); the posterior half of the head capsule almost entirely smooth and shiny; and the postpetiolar node seen from above oval, elliptical, or laterally angulate (cornulate in cerebrosior HNS ). P. ceres HNS is distinguished within the complex by the following combination of traits. Dark to blackish brown. Major: carinulae originating on the frontal triangle travel along the midline to the occiput; transverse carinulae present along the anterior lateral margins of the pronotum; mesonotal convexity and propodeal spines well-developed; postpetiole from above laterally angulate and diamond-shaped.
Minor: eyes moderately large; mesonotal convexity low but well-developed. Measurements (mm) Lectotype major: HW 1.14, HL 1.18, SL 0.66, EL 0.16, PW 0.54. Paralectotype minor: HW 0.54, HL 0.60, SL 0.54, EL 0.12, PW 0.34.
Color Major: body blackish brown, with brownish yellow clypeus; appendages brownish yellow to medium brown. Minor: like the major, except that the clypeus is not yellow but dark brown and hence not contrasting.
Range Foothills of the Rockies in eastern Colorado at 1800-2600 m, southwest to the mountains of New Mexico and Arizona, at 2200-2700 m, as well as extreme eastern Nevada. Also recorded from the Davis Mts. of Texas but evidently rare there (Creighton 1950a: 174), and from Guerrereo Mills, in the mountains of Hidalgo ( tepaneca HNS types).
biology According to Stefan Cover, ceres HNS is found at higher elevations and in colder climates than any other Pheidole HNS species in the western North American fauna. In southern Arizona it is often the only Pheidole HNS occurring above 2250 m. Gregg (1963) reports ceres HNS to be the most abundant Pheidole HNS in Colorado, where it occurs in a wide array of habitats, including ponderosa pine forest, foothills meadowland, and sagebrush. Cover found the species in the same general habitats in Arizona and New Mexico. In Nevada G. C. and J. Wheeler (1986g) found a colony at 2650 m in juniper-pinyon woodland. The ants collect and store seeds of a variety of grasses and herbaceous angiosperms. P. ceres HNS nests in several types of open soil under rocks. Colonies are large and active, consisting of up to 1000 ants. Majors are numerous and most colonies are monogynous. P. ceres HNS is also notable as the host of the workerles parasite P. elecebra HNS . Winged sexuals have been found in nests principally from early to the middle of July, with one record of males on 9 September. Winged reproductives have been found in nests throughout July, and a wingless queen was collected on 21 July, presumably following a nuptial flight.
Figure Upper: lectotype, major. Lower: paralectotype, minor. COLORADO: Colorado Springs (W. M. Wheeler). Scale bars = 1 mm.