Solenopsis krockowi

This species nests under stones in dry shrubland including sparse mesquite scrub on rocky slopes. Specimens were collected in a variety of leaf litter, ranging from desert scrub (creosotebush) to cottonwood tree leaves. Brood and sexuals were found in a nest in June (Mexico), and it has been collected in surface and subterranean Vienna sausage baits, and in pitfall traps. (Pacheco and Mackay 2013)

Identification
A New World thief ant that is a member of the fugax species complex

Pacheco and Mackay (2013) – Worker - This is a relatively large, bright yellow species, with coarse cephalic punctures. The head is nearly quadrate, a little longer than wide. The clypeal teeth are widely spaced, with a distance of about 0.100 mm between the tips of the teeth. The extralateral teeth are often well developed. It has a large, extended subpeduncular process; the postpetiole is oval-shaped as seen from above and has a large flange ventrally. Queen The queen is very large, over 7 mm in total length. It is golden yellow with the head wider than long and coarsely punctate. Four clypeal teeth are present and well developed, while the clypeal carinae are weakly defined. The pronotum is coarsely punctate and horizontal striae are present on the metapleuron.

Solenopsis krockowi could be confused with the widely distributed Solenopsis molesta, but is easily separated by its rectangular-shaped head. The punctures on the head are very coarse, whereas they are fine in S. molesta. It can be separated from Solenopsis pergandei (southern USA) on the basis of the oval-shaped postpetiole (round in S. pergandei). The widely diverging clypeal carinae separate it from Solenopsis pilosula (Texas), in which the carinae are nearly parallel and closely spaced. The widely spaced clypeal carinae and monomorphism separate it from the similar Solenopsis johnsoni (Mexico) and Solenopsis vinsoni (Central America).

Keys

 * Key to New World Solenopsis Species Complexes
 * Key to Solenopsis fugax species complex / Clave a las obreras del complejo Solenopsis fugax

Distribution
United States: Arizona, New Mexico and Texas. Mexico: San Luis Potosi.

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

Habitat
Chihuahuan Desert scrub, riparian, juniper, sagebrush, urban habitats. (Mackay and Mackay 2002)

Biology
Solenopsis krockowi nests under stones, or simply in the soil with no external evidence of the nest. This species is predominantly subterranean. Sexuals were found in nests in July and August. Foragers can be captured with subterranean traps in southern NM. (Mackay and Mackay 2002)

Nomenclature

 *  krockowi. Solenopsis krockowi Wheeler, W.M. 1908e: 428, pl. 26, figs. 28, 29 (w.q.) U.S.A.

Worker
Pacheco and Mackay (2013) - Measurements (n=5). TL 2.22-2.34 (2.29); HL 0.564-0.600 (0.575); HW 0.510-0.570 (0.533); EL 0.060-0.066 (0.062); ED 0.042; SL 0.396-0.444 (0.412); FSL 0.186-0.198 (0.191); CI 90.4-95.0 (92.7); SI 70.2-74.0 (71.6); PL 0.102-0.120 (0.106); PW 0.168-0.180 (0.170); PI 60.7-66.7 (61.9); PPL 0.132-0.150 (0.137); PPW 0.174-0.192 (0.180); PPI 73.3-79.3 (75.9); WL 0.420-0.480 (0.443); PSL 0.042-0.048 (0.044); PSW 0.042-0.048 (0.043).

Moderately large, concolorous yellow; head longer than wide, coarsely punctate; clypeallateral teeth widely spaced, distance of 0.1 0 mm between tips of teeth; extralateral teeth often well developed; clypeal carinae well defined; eyes small, 5-6 ommatidia; mesosoma smooth and shiny, pronotum with coarse punctures; notopropodeal suture well depressed; posterior propodeal margin rounded; propodeal spiracle large; extended subpeduncular process large; petiole oval-shaped viewed dorsally, with large flange at subpeduncular process; postpetiolar node globose, without flange or tooth ventrally.

Hairy with erect and sub erect hairs of various lengths on all body surfaces; cephalic hairs short, central portion of head without hair; hairs on remainder of body, including petiole and postpetiole, mixture of long (0.070 mm) and short (0.040 mm) hairs.

Queen
Pacheco and Mackay (2013) - Measurements (n=1). TL 7.32; HL 0.990; HW 1.02; EL 0.360; ED; 0.252; MOL 0.114; MOD 0.108; SL 0.720; FSL 0.540; CI 102; SI 35.3; PSL 0.120; PSW 0.090; PL 0.138; PW 0.420; PI 32.9; PPL 0.360; PPW 0.480; PPI 75.0; WL 1.80.

Very large, concolorous golden yellow; head quadrate, slightly wider than long, narrowed anteriorly, coarsely punctate; lateral clypeal teeth well developed; space between lateral teeth wide at 0.210 mm; extralateral teeth well developed; scapes long, do not reach posterior lateral corner of head; minor funicular segments long; eyes large; medial ocellus large; pronotum coarsely punctate; mesopleuron smooth and shiny; metapleuron horizontally striated; posterior propodeal margin rounded; propodeal spiracle large; petiole wider than postpetiole viewed laterally; large flange ventrally on petiolar peduncle; both petiole and postpetiole striated basally on nodes.

Abundantly hairy, pilosity yellow; erect and suberect hairs covering all body surfaces.

Type Material
New Mexico, Sacramento Mts., Box Canon, 06-vii-1906, Wheeler, type, Von Krockow type #1-13 20907 (lectotype worker, 6 paralectotype workers and 1 paralectotype queen [here designated] ).