Crematogaster crinosa

A widespread, common species that can form large colonies. Crematogaster crinosa is found across a range of habitats but the largest colonies are found in dryer areas such as seasonally dry forest. Their polydomous nests can be found in just about all the available cavities, i.e., any protected space, in the trees they occupy.

Identification
Longino (2003) - Members of the crinosa-complex are among the most frequently encountered Neotropical ants, particularly in open or seasonally dry habitats. They are geographically variable and taxonomically difficult, and species boundaries are poorly defined. Crematogaster crinosa, Crematogaster rochai, and Crematogaster torosa are three very similar species that occur together in Costa Rica. They are difficult to distinguish and workers may not always be clearly identified. All three have the face with sparse erect setae over short appressed pubescence, the mesosomal dorsum and fourth abdominal tergite with short, stiff erect setae (or erect setae absent), the dorsal face of the petiole short with convex sides, and the propodeal spines short and upturned. Crematogaster crinosa can be differentiated from rochai throughout the range, because crinosa has a dense, even covering of erect setae on the fourth abdominal tergite, while rochai completely lacks these setae or has only a small cluster on each anterolateral humerus. Distinguishing crinosa from torosa is more difficult. In Costa Rica, torosa also has abundant erect setae on the fourth abdominal tergite, but these are usually clustered laterally and anterolaterally, leaving a median strip free of setae. Also, crinosa always has a long, sharp anteroventral petiolar process, while torosa more often has a short, blunt or squared-off process. Crematogaster crinosa can also be confused with Crematogaster erecta and Crematogaster moelleri, but these have flexuous erect setae on the pronotal humeri.

Distribution
Longino (2003) - Throughout the Neotropics, from southern Texas to Argentina and on numerous Caribbean islands.

Distribution based on Regional Taxon Lists
Nearctic Region: United States. Neotropical Region: Argentina, Barbados, Belize, Bolivia, Brazil, Chile, Colombia, Costa Rica, Ecuador, French Guiana, Greater Antilles, Grenada, Guatemala, Guyana, Honduras, Lesser Antilles, Martinique, Mexico, Nicaragua, Panama, Paraguay, Peru, Suriname, Trinidad and Tobago, Uruguay, Venezuela.

Biology
Longino (2003) - Crematogaster crinosa is an extremely widespread and generalized species that prefers highly insolated habitats. It is common in seasonally dry areas, less common in wet forests. In wet forest habitats it is typically found in the high canopy or in disturbed areas. It may form monodominant populations in mangrove forests.

Colonies are large and polydomous and it is usually difficult to locate colony boundaries. Nests are found in almost any kind of cavity, and columns of workers move from nest to nest. Nests can be in live or dead branches, in small rotten knots, under bark flaps, in cavities in fence posts, opportunistically in ant plants, and thinly dispersed in multiple small bark cavities. Workers, brood, and alate sexuals are dispersed across nests. Small amounts of carton construction are used to form baffles inside of nest cavities and to restrict nest entrances, but large external carton nests are never constructed.

Although new alate queens are relatively common in nests, I have rarely encountered physogastric colony queens. In my collecting experience, I have never found a colony that was obviously polygynous, with many dealate queens dispersed in many nests. However, I am treating Forel's minutior as a synonym of crinosa, and minutior from St. Vincent Island in the West Indies forms large polygynous, polydomous colonies in coastal areas (Forel 1893).

In Colombia I observed the beginning of a nuptial flight just after dusk. I found a dense aggregation of males and workers under a bark flap, and the males were just beginning to fly.

Workers are omnivorous. They are attracted to protein and carbohydrate baits, they scavenge dead or injured insects, they visit extrafloral nectaries, and they tend Homoptera. When nests are disturbed they can be aggressive and will bite. Workers are continuously polymorphic, with a broad range of worker sizes.

Ecological equivalents are torosa and rochai. I can detect very few behavioral or ecological differences among these species. Crematogaster crinosa is the only member of the group that regularly dominates mangrove habitats. Mangrove forests in Costa Rica are sometimes dominated by Azteca, sometimes by C. crinosa. I found a similar situation in the Santa Marta area of Colombia. I have only one record of rochai from mangroves (a voucher collection from Adams' studies of mangrove communities, Adams 1994), and I have no record of torosa from mangroves. Other than in mangroves, crinosa is less abundant relative to torosa or rochai. For example, a collecting trip to a wildlife refuge in southern Texas yielded 13 separate collections of torosa but only one of crinosa. In northwestern Costa Rica, torosa and rochai are far more abundant than crinosa. Based on museum collections, crinosa seems to be the most common member of the crinosa group on various Caribbean and Pacific islands.

 Gillette et al. (2015) in a Chaipas, Mexico field study of twig-nesting ants in coffee plants found C. crinosa nesting on plants between 1150-1450 m in elevation.

Nomenclature

 *  crinosa. Crematogaster crinosa Mayr, 1862: 767 (w.) BRAZIL. Mayr, 1887: 627 (q.m.). Combination in C. (Orthocrema): Emery, 1922e: 134. Senior synonym of brevispinosa, chathamensis, minutior, recurvispina, sampaioi, schuppi, striatinota, townsendi and material of the unavailable name semisericea referred here: Longino, 2003a: 49.
 * brevispinosa. Crematogaster brevispinosa Mayr, 1870a: 403 (w.) COLOMBIA. Wheeler, G.C. & Wheeler, J. 1952b: 260 (l.). Combination in C. (Orthocrema): Santschi, 1918d: 182. Junior synonym of crinosa: Longino, 2003a: 49.
 * minutior. Crematogaster brevispinosa var. minutior Forel, 1893g: 399 (w.q.) ANTILLES. Combination in C. (Orthocrema): Emery, 1922e: 134. Subspecies of brevispinosa: Forel, 1897b: 300. Junior synonym of crinosa: Longino, 2003a: 49.
 * schuppi. Crematogaster brevispinosa var. schuppi Forel, 1901d: 299 (w.q.) BRAZIL. Combination in C. (Orthocrema): Emery, 1922e: 134. Junior synonym of crinosa: Longino, 2003a: 49.
 * recurvispina. Crematogaster brevispinosa r. recurvispina Forel, 1912f: 212 (w.) BRAZIL. Combination in C. (Orthocrema): Emery, 1922e: 134; Santschi, 1925d: 230. Junior synonym of crinosa: Longino, 2003a: 49.
 * sampaioi. Crematogaster brevispinosa r. sampaioi Forel, 1912f: 213 (w.q.m.) BRAZIL. Combination in C. (Orthocrema): Emery, 1922e: 134. Junior synonym of crinosa: Longino, 2003a: 49.
 * striatinota. Crematogaster brevispinosa var. striatinota Forel, 1912f: 211 (w.) COLOMBIA. Junior synonym of crinosa: Longino, 2003a: 49.
 * townsendi. Crematogaster (Orthocrema) brevispinosa subsp. townsendi Wheeler, W.M. 1925a: 25 (w.) PERU. Junior synonym of crinosa: Longino, 2003a: 49.
 * chathamensis. Crematogaster (Orthocrema) brevispinosa subsp. chathamensis Wheeler, W.M. 1933a: 58 (w.) ECUADOR (Galapagos Is). Junior synonym of crinosa: Longino, 2003a: 49.

Longino (2003) - Synonyms: The workers of Crematogaster recurvispina are small, with few setae on mesosoma and fourth abdominal tergite, and a strong anteroventral petiolar tooth. These may just be small workers of crinosa. A brief examination of the schuppi types revealed a queen and a minim worker. The queen had a strong anteroventral petiolar tooth, was abundantly setose, and had a quadrate head. It is probably crinosa. The other synonymies are all based on examination of medium-size to large workers that match the general features of crinosa as defined here.

Worker
Wheeler (1933) for Crematogaster brevispinosa chathamensis - Length 2.5-3.3 mm.

Head slightly broader than long in the largest specimens, with slightly concave posterior border. Eyes elongate, flattened, near the middle of the sides. Clypeus convex, with nearly straight, transverse anterior border. Antennal scapes not reaching to the posterior border of the head; funiculi with distinctly 2•jointed club; basal funicular joints, except the first, broader than long. Thorax short; pro- and mesonotum convex and hemispherical; mesoepinotal impression short and deep; base of epinotum short, anteriorly very convex and rising rather abruptly from the impression; declivity much longer, sloping; spines suberect, much shorter than their distance apart at the base, their tips slender and acute, sometimes slightly recurved. Petiole somewhat longer than broad, subelliptical, as broad behind as in front, with rounded sides and distinctly dentate posterior corners, anteroventrally with a strong spine, directed forward and downward. Postpetiole short and convex, narrower than the petiole, without median dorsal groove. Legs rather short and stout.

Mandibles, clypeus, front, gula and sides of head finely, longitudinally striate; posterior portion of head smooth and shining, with sparse piligerous punctures. Thorax subopaque, only the epinotal declivity shining; pronotum transversely, mesonotum and base of epinotum longitudinally striate; meso- and metapleurae evenly and densely punctate. Petiole and postpetiole shining, the former smooth above and coarsely reticulate below, the latter delicately longitudinally rugulose. Gaster subopaque, finely punctate.shagreened.

Hairs pale, sparse, blunt and erect on the thorax, pedicel and gaster; head, scapes and gaster with long, sparse, appressed pubescence; legs with similar but finer pubescence.

Large workers red, with the thorax and posterior portion of the gaster black; trochanters and tarsi yellow; smaller workers darker, blackish, with mandibles, antenne, tibiae and tarsi reddish; trochanters yellow.

Longino (2003) - HL 0.801, 0.616, 1.052; HW 0.869, 0.701, 1.156; HC 0.837, 0.664, 1.123; SL 0.537, 0.454, 0.697; EL 0.175, 0.147, 0.252; A11L 0.248; A11W 0.138; A10L 0.097; A10W 0.113; A09L 0.055; A09W 0.078; A08L 0.034; A08W 0.066; WL 0.844, 0.688, 1.146; SPL 0.134, 0.095, 0.168; PTH 0.174, 0.142, 0.203; PTL 0.239, 0.206, 0.343; PTW 0.253, 0.224, 0.323; PPL 0.198, 0.182, 0.254; PPW 0.246, 0.205, 0.328; CI 108, 114, 110; OI 22, 24, 24; SI 67, 74, 66; PTHI 73, 69, 59; PTWI 106, 109, 94; PPI 124, 113, 129; SPI 16, 14, 15; ACI 0.64.

Color red brown to black; workers usually with pronounced size polymorphism. In face view head subquadrate, wider than long in larger workers, with emarginate posterior margin; mandibles coarsely striate, striae faint to pronounced; clypeus smooth and shiny or faintly granular or finely longitudinally striate; scapes short, in face view not attaining posterior margin of head when laid back; terminal three segments of antenna gradually lengthening and broadening, becoming increasingly densely pubescent, terminal two segments very much larger, so that antennal club appears two-segmented; scapes with short appressed pubescence, sometimes subdecumbent, never erect, with no differentiated long erect setae (occasionally a long seta on very large workers); face with sparse appressed to subdecument pubescence and sparse short erect setae; face smooth and shining or with variably developed fine longitudinal striation, most common on anterior face and space between eye and antennal insertion, occasionally extending posteriorly and medially, but always with at least median strip sublucid.

Promesonotal profile forming a single, somewhat flat-topped convexity; in large workers promesonotal suture visible, a dorsolateral arch that extends far forward, showing that dorsal pronotum is short and much of promesonotal dorsum composed of mesonotum (approaching queen condition); in small workers promesonotal suture effaced, visible only as oblique anterolateral impressions; propodeum with short but distinctly differentiated dorsal face, such that propodeal suture distinctly visible in lateral view as v-shaped impression; propodeum with long sloping posterior face; propodeal spines short, upturned; promesonotal dorsum and dorsal face of propodeum faintly punctate with varying development of longitudinal or transversely whorled rugulae or striations, lateral carinulae bridge propodeal suture, rarely forming a small triangular denticle; posterior face of propodeum smooth and shining or faintly microareolate; lateral pronotum with faint microsculpture; katepisternum and lateral propodeum faintly punctate to microareolate; promesonotum and bases of propodeal spines with highly variable number but usually abundant short stiff flattened setae; femora and tibiae with appressed to subdecumbent pubescence, no erect setae.

Petiole in lateral view subtriangular, often with slightly concave ventral margin, with strongly developed, anteriorly projecting, acute anteroventral tooth; side faintly granular or microareolate; dorsal face of petiole smooth and shining to faintly microareolate, about as wide as long, subquadrate or more often with convex sides, widest about one third distance from anterior margin, with one or more stiff setae on posterolateral tubercles; postpetiole with no ventral tooth, in dorsal view globular to subquadrate, usually slightly broader than long, rarely with faintly impressed posteromedian sulcus, with four or more stiff setae; fourth abdominal tergite smooth and shining or faintly microareolate, with abundant vestiture of short, stiff, flattened, erect setae, evenly distributed over surface of tergite (not clustered or concentrated 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
Crematogaster brevispinosa chathamensis Described from ten workers taken on Chatham Island (IV.17.'32). Lectotype, C. A. S. Ent. No. 3689.

Longino (2003) - Syntype workers: Brazil, Rio de Janeiro (Novara) (examined).