Pogonomyrmex maricopa

The habits of Pogonomyrmex maricpa and Pogonomyrmex californicus can be very similar. Nest type, habitat, colony strength, and foraging behavior are often nearly identical. But, whereas californicus seems always to construct a semicircular or circular sand crater, maricopa nests may be surmounted by sand or pebble craters or sand domes with a surface covering of gravel. Both species nest in open areas. (Cole 1968)

Identification
Cole (1968) - P. maricopa has an extensive range not only in longitude but also in latitude, for it extends from southern Colorado to well within Sonora, Sinaloa, and Chihuahua, Mexico. The typical form is abundant in southern New Mexico. The workers of this population have either an unarmed epinotum or one with angles or short spines, as do also the types of maricopa from Alamogordo, New Mexico (Pl. VI, Fig. 11). But maricopa s. l. exhibits a considerable degree of intraspecific variation.

The closest relative of Pogonomyrmex maricopa seems to be Pogonomyrmex californicus. Creighton (1950. p. 127) refers to the cephalic sculpture of maricopa as being "heavy and dense" and to the thoracic sculpture as being "heavier than that of californicus." If he means by "heavy" a coarser rugosity, I cannot agree with him; for when one compares the rugae of maricopa with those of californicus, those of the latter are certainly coarser. The "typical" maricopa worker with its closely spaced, comparatively fine cephalic rugae and densely punctate interrugal spaces is in strong contrast with the " typical" californicus worker with widely spaced, coarse rugae and smooth, strongly shining interrugal areas. Densely punctate californicus workers, however, are often difficult to separate from those of maricopa; the converse is also true. In such specimens the conformation of the mandible, scape base, thorax, petiole, and postpetiole may be quite similar. Rugosity and color may be virtually the same; but the thoracic dorsum of maricopa is generally more uneven, and invariably, it seems, the sides of the epinotum bear at least some distinct punctures, whereas those of californicus are smooth and shining.

The sexes of the two species are more readily distinguishable from each other. In the female of maricopa the interrugal spaces of the head bear faint to prominent punctures; in the Pogonomyrmex californicus female these spaces are smooth and strongly shining. The mandible of the Pogonomyrmex maricopa male generally bears 4 or 5 teeth, whereas that of the californicus male usually has only 2 or 3. In any caste, if the epinotum bears armature the specimen is not referable to californicus. Such specimens are readily identifiable; but, unfortunately, maricopa is commonly completely unarmed. It is indeed usually true, as Creighton (1950, p. 127) states, that "the epinotum of maricopa is more angular than that of californicus" in the worker caste; but the difference is sometimes more subtle than the words indicate.

Pogonomyrmex comanche, to which maricopa is also closely related, is easily distinguishable from maricopa by its flattened and generally longitudinally depressed dorsum of the petiolar node which bears strong, usually transverse rugae.

Distribution
United States: western Texas, New Mexico, southern Colorado, southern Utah, Arizona, southeastern Nevada, southeastern California. Mexico: Sinaloa, Sonora, northern Chihuahua, northern Baja California.

Distribution based on Regional Taxon Lists
Nearctic Region: United States. Neotropical Region: Mexico.

Habitat
This species is found in all communities of the Chihuahuan Desert, especially areas with sandy soils. This is one of the few species which can nest in loose sands, such as at White Sands National Monument. (Mackay and Mackay 2002)

Biology
This species usually has nests very similar to those of Pogonomyrmex californicus, and usually occurs in sandy soils. In some areas, for example the sandy soils east of El Paso, TX, the nests are immense, with clearing up to 7 meters in diameter with the mounds approaching 2 meters in height. Typical nests are also found in the same area. Unfortunately most of these nests have been eliminated by urbanization, and will probably be completely eliminated in the future. These ants are extremely pugnacious and have a very painful sting. Flights occur from June to August, new colonies are formed in July - October. They are individual foragers collecting seeds, excrement and dead insects. The myrmecophilous scarabaeid beetle genus Cremastocheilus occurs in the nests. (Mackay and Mackay 2002)

Nevada, Wheeler and Wheeler (1986) - We have 16 records from 13 localities in the southern part of the state; 500-3,400 ft. All are from the Hot Desert (1 from a cottonwood grove and 2 from disturbed areas). The superstructure of 3 nests consisted of gravel. One was a large (51 x 91 cm) irregular mound with 3 horizontal slit-like entrances; 2 had piles of tailings below slit-like entrances. The piles of tailings fanned out to 38 cm and 61 cm; the entrances were 12 mm high and 38 mm wide.

Whitford (2003) found that Pogonomyrmex maricopa constructed cemented caps on their sand mound nests in a fine sand dune area. The caps are approximately 60% calcium carbonate that is transported from the underlying calcium carbonate layers. The caps protect the nest structure from being eroded away during high-wind periods and partial erosion of the cemented caps adds calcium carbonate to the sand dune soils.

Nomenclature

 *  maricopa. Pogonomyrmex californicus subsp. maricopa Wheeler, W.M. 1914e: 155 (w.q.) U.S.A. Cole, 1968: 140 (m.); Taber, Cokendolpher & Francke, 1988: 51 (k.). Raised to species: Creighton, 1950a: 126. Senior synonym of barnesi: Cole, 1968: 138; of sinaloanus: Brown, in Cole, 1954b: 120.
 * barnesi. Pogonomyrmex californicus subsp. barnesi Smith, M.R. 1929: 546 (w.) U.S.A. Subspecies of maricopa: Creighton, 1950a: 127. Junior synonym of maricopa: Cole, 1968: 138.
 * sinaloanus. Pogonomyrmex californicus subsp. sinaloanus Olsen, 1934: 504 (w.) MEXICO. Junior synonym of maricopa: Brown, in Cole, 1954b: 120.

Worker
Cole (1968) - HL 1.60-2.05 mm, HW 1.52-2.05 mm, CI 95.0-102.2, SL 1.22-1.56 mm, SI 76.1-80.3, EL 0.38-0.46 mm, EW 0.27-0.30 mm, OI 20.2-24.2, WL 1.90-2.44 mm, PNL 0.46-0.61 mm, PNW 0.42-0.57 mm, PPL 0.46-0.61 mm, PPW 0.53-0.72 mm.

Conrormation of mandible as shown in Pl. III, Fig. 10; all teeth long, well separated, rather strongly acute; apical tooth considerably longer than subapical; first basal tooth only a little shorter than subapical, longer than second basal; length of second, third, and ultimate basals subequal; penultimate basal distinctly shorter than ultimate, meeting the basal mandibular margin at a straight angle.

Base of antennal scape as illustrated in Pl. IV, Fig. 7; basal enlargement very weak, superior lobe undeveloped, inferior lobe weakly developed; superior lobe with a very short declivity, the shaft meeting the prominent but very thin basal flange at a strong angle; basal flange curved distad, extending along scape base from lip to apex of superior lobe from which it is directed distinctly outward, lip narrow, extending outward for only a short distance curved slightly distad, its outer margin thin; basal impression shallow but distinct because of steep declivities that enclose it; longitudinal peripheral carina and point very weak to absent.

Cephalic rugae fine, father closely spaced; interrugal areas densely punctate and subopaque or opaque. Conformation of thorax, petiole, and postpetiole as in Pl. VI. Fig. 11; thoracic contour similar to that of californicus but more irregular, the sutures more marked, and especially the mesoepinotal suture distinctly and frequently broadly impressed. Peliole and postpetiole, in dorsal view, as shown in PI. VII, Fig. 7. Epinotum, in lateral view, distinctly angular; without armature or with a pair of angles, denticles, or short to long spines. Thorax. including sides of epinotum, densely and prominently punctate; rather finely rugose, subopaque or opaque. Shape of petiolar node variable, nipple absent to strong. Petiolar node strongly shagreened or punctate. shining or dull, often with a few unevenly spaced rugae or striae. Ventral process of petiolar peduncle absent to moderately strong. Postpetiolar node shagreened or punctate, shining or subopaque; sometimes bearing weak, irregular striae with a transverse trend. Ventral process of postpetiole weakly to moderately developed. Gaster moderately to strongly shining. densely and very finely shagreened. Body color light to very deep ferrugineous red.

Queen
Cole (1968) - HL 1.98-2.28 mm, HW 2.09-2.32 mm, CI 101.0-109.1, SL 1.52-1.60 mm. SI 68.4-72.7, EL 0.46-0.49 mm, EW 0.30-0.38 mm. OI 21.1-23.4, WL 3.04-3.42 mm. PNL 0.53-0.65 mm, PNW 0.61-0.68 mm. PPL 0.61-0.76 mm. PPW 0.99-1.14 mm.

Similar to the worker and with the usual female characters. Interrugal spaces of head and thorax moderately shining to subopaque; cephalic interrugal punctation rather faint; entire thorax densely and rather finely rugose; interrugal punctation on sides of epinotum weak to strong, distinct. Epinotum generally unarmed, sometimes with a pair of tubercles. Dorsum of petiolar node, in lateral view, weakly to moderately convex, not impressed. Postpetiolar node notably broader than long. Body color medium to deep ferrugineous red, the gaster sometimes infuscated.

Male
Cole (1968) - HL 1.37-1.63 mm, HW 1.63-1.82 mm, CI 111.6-118.9, SL 0.68-0.91 mm, SI 49.6-55.8, EL 0.57-0.61 mm, EW 0.30-0.42 mm, OI 39.0-41.6, WL 3.04-3.15 mm, PNL 0.46-0.57 mm, PNW 0.66-0.80 mm, PPL 0.65-0.80 mm, PPW 0.87-1.03 mm.

Mandible as shown in Pl. VIII. Fig. 7; with 3 to 5 (usually 4 or 5) teeth. Antennal scape either only slightly or not at all longer than combined lengths of pedicel and first three flagellar segments. Head rather uniformly, finely, and densely rugose; with a distinct, longitudinal carina extending from midoccipital margin to just behind ocelli. Anterior declivity of pronotum, in lateral view, concave, meeting the pronotal collar at a well-rounded angle. Epinotum unarmed or with a pair of angles, tubercles, or short spines. Ventral process of postpetiole very weak. Thorax, except epinotum, mostly finely rugose; epinotum smooth and shining. Interrugal spaces of head and thorax largely without punctures; shining or subopaque. Dorsum of petiolar node weakly to strongly impressed. Petiolar and postpetiolar nodes and gaster smooth and shining; gaster not shagreened. Paramere as shown in Pl. X. Fig. 8 and Pl. XI. Fig. 8. Head. Thorax, petiole, and postpetiole deep brownish black; gaster, antennae, and leg extremities notably lighter; first segment of gaster often infuseated basally.