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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 " bicarinataHNS complex" of the larger piliferaHNS group, comprising agricolaHNS, aureaHNS, barbataHNS, bicarinataHNS, centeotlHNS, cerebrosiorHNS, ceresHNS, defectaHNS, gilvescensHNS, macclendoniHNS, macropsHNS, marcidulaHNS, paiuteHNS, pinealisHNS, psammophilaHNS, vinelandicaHNS, xerophilaHNS, yaquiHNS, and yucatanaHNS, 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 aureaHNS); 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 cerebrosiorHNS). P. ceresHNS 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 ( tepanecaHNS types).
biology According to Stefan Cover, ceresHNS is found at higher elevations and in colder climates than any other PheidoleHNS species in the western North American fauna. In southern Arizona it is often the only PheidoleHNS occurring above 2250 m. Gregg (1963) reports ceresHNS to be the most abundant PheidoleHNS 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. ceresHNS 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. ceresHNS is also notable as the host of the workerles parasite P. elecebraHNS. 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.
Found most commonly in these habitats: 4 times found in shrub steppe, 2 times found in Under rock, Mixed canyon forest, 3 times found in gambel oak/grassland, 4 times found in Pinyon-juniper-oak-woodland, 1 times found in sagebrush/pinyon juniper, 3 times found in conifer woodland, 1 times found in Meadow, Under rock, 1 times found in gambel oak scrub, 1 times found in Ponderosa pine-oak forest, 2 times found in Under rock, Pinyon-cedar-oak woodland, ...
Found most commonly in these microhabitats: 19 times under rock, 13 times under stone, 2 times nocturnal foragers, 2 times at bait * at night, 1 times nest in soil, 1 times suelo, debajo de una piedra, 1 times nido en suelo, debajo piedra, 1 times nest under rock on rock face, 1 times foraging on hilltop, 1 times worker on rock face, 1 times worker in soil on rock face, ...
Collected most commonly using these methods: 17 times search, 2 times bait, 2 times Directo, 1 times direct collection.
Elevations: collected from 135 - 2725 meters, 2012 meters average