Crematogaster torosa

An arboreal species that can form large polydomous colonies.

Identification
Longino (2003) - This is a member of the Crematogaster crinosa-complex and may not always be distinguishable from crinosa and Crematogaster rochai. See under crinosa for further discussion.

Specimens of torosa from the northern end of the range, in southeast Texas and in Arizona, are somewhat smaller and less polymorphic than Costa Rican material, but this seems to gradually change as one moves northward in Mexico. Specimens from Baja California are bicolored, with reddish head and mesosoma, and black gaster. However, the abundant material from Arizona and Costa Rica shows continuous variation in the degree of infuscation of the head and mesosoma, and some material may be clearly bicolored like the Baja material. Specimens from Baja nearly always have a long, acute anteroventral petiolar tooth. Specimens from the state of Arizona in the USA and Sonora and Sinaloa states in Mexico (former Crematogaster arizonensis) usually have a short but sharply acute tooth as an average condition, but the tooth form varies from long and spine-like to short and right angled. Specimens from southeastern Texas and Costa Rica show a great deal of variability, but usually have a right-angle tooth and less often a short, sharply acute tooth. They never have a long spine-like tooth. For the time being I interpret all this material as torosa, differing from crinosa and rochai by the somewhat flatter promesonotum and the usually shorter petiolar tooth, and with a gastral setal pattern intermediate between crinosa, which has a uniform covering of flattened setae, and rochai, which has no erect setae.

Distribution
USA at least to Colombia, southern limit of species range not defined.

Distribution based on Regional Taxon Lists
Nearctic Region: United States. Neotropical Region: Argentina, Bolivia, Brazil, Colombia, Costa Rica, Guatemala, Honduras, Mexico, Nicaragua, Panama, Paraguay.



Biology
Longino (2003) - Crematogaster torosa has a biology very similar to Crematogaster crinosa and Crematogaster rochai. It occurs primarily in open, seasonally dry areas, highly disturbed areas, and pasture edges, although it can also be found in the canopy of mature wet forest. In Costa Rica it is a common species in urban areas such as the various city parks in the capital, San José.

Nests are large, polydomous, distributed in a wide variety of plant cavities. Dead branches and knots in living trees are most often used. In Guanacaste Province in Costa Rica they often occupy ant acacias, and may invade acacias already occupied by Pseudomyrmex. They often construct small carton baffles that restrict nest entrances and small carton pavilions that shelter Homoptera on surrounding vegetation. In some instances they may inhabit cavities in live stems. I found a large nest in the live stems of a Protium branch (Burseraceae) in Corcovado National Park, and I have found nests in live stems of myrmecophytic Acacia and Triplaris. Nest chambers are sometimes filled with alate queens and males. Based on a sample size of two, colony founding is monogynous. In one case I dissected a small colony in south Texas and found a single physogastric queen in the center. In another case I found a lone foundress queen in a dead branch of a Triplaris tree in Costa Rica.

Foraging is primarily diurnal but occasional nocturnal foragers are seen. Workers are generalized scavengers and they frequently visit extrafloral nectaries. Often columns of workers move between nests.

New Mexico
Mackay and Mackay (2002) - This species nests in the soil, in mistletoe and branches of oak trees, mesquite trees or palo verde trees, or under roots of cottonwood trees. Some of the workers are larger and specialized for producing unfertilized eggs, which are fed to the queen or brood, or develop into males. The specimens from New Mexico were collected under oaks along a trail.

Nomenclature

 *  torosa. Crematogaster torosa Mayr, 1870a: 404 (w.) COLOMBIA. Combination in C. (Orthocrema): Emery, 1922e: 136; Santschi, 1925d: 229. Senior synonym of arizonensis, tumulifera: Longino, 2003a: 120.
 * tumulifera. Crematogaster brevispinosa var. tumulifera Forel, 1899c: 84 (w.) NICARAGUA. Forel, 1908b: 47 (q.m.); Wheeler, G.C. & Wheeler, J. 1952b: 260 (l.). Combination in C. (Orthocrema): Emery, 1922e: 134. Subspecies of brevispinosa: Forel, 1907a: 25; Forel, 1908c: 369; Forel, 1909a: 258; Forel, 1912f: 215. Junior synonym of torosa: Longino, 2003a: 120.
 * arizonensis. Crematogaster arizonensis Wheeler, W.M. 1908e: 482, pl. 27, fig. 40 (w.) U.S.A. Wheeler, W.M. 1912b: 132 (q.m.). Combination in C. (Orthocrema): Emery, 1922e: 134. Junior synonym of torosa: Longino, 2003a: 121.

Worker
Longino (2003) - (Costa Rica) HL 0.682, 0.578, 1.045; HW 0.763, 0.629, 1.179; HC 0.760, 0.598, 1.123; SL 0.488, 0.443, 0.706; EL 0.170, 0.130, 0.259; A11L 0.241; A11W 0.140; A10L 0.118; A10W 0.118; A09L 0.060; A09W 0.085; A08L 0.041; A08W 0.071; WL 0.789, 0.664, 1.269; SPL 0.080, 0.057, 0.142; PTH 0.165, 0.129, 0.280; PTL 0.232, 0.175, 0.380; PTW 0.246, 0.180, 0.373; PPL 0.171, 0.150, 0.265; PPW 0.224, 0.189, 0.371; CI 112, 109, 113; OI 25, 22, 25; SI 72, 77, 68; PTHI 71, 74, 74; PTWI 106, 103, 98; PPI 131, 126, 140; SPI 10, 9, 11; ACI 0.98.

Differing from Crematogaster crinosa in the following respects: mesonotum shorter, promesonotal suture more often impressed, making promesonotal profile flatter; anteroventral petiolar tooth shorter, more often forming nearly right angle rather than long acute tooth; setae on fourth abdominal tergite less abundant, especially medially, such that erect setae more dense anterolaterally.

Queen
Longino (2003) - A normal queen (dorsal face of propodeum drops steeply from postscutellum and much of propodeum appears ventral to scutellum and postscutellum) with general shape, sculpture, and pilosity characters of the worker; size characters as in Figures.

Type Material
Longino (2003) - Syntype workers: Colombia, Santa Fe de Bogotá (Lindig) (examined).