Crematogaster arcuata

The relatively few collections of this species have been from forested sites, sea level to 1000m elevation, in moist to wet forest habitats and cerrado. The only known Costa Rican collection is from the Osa Peninsula. The one nest I have observed was on a roadside in Venezuela. It was in an area of small farms and coffee plantations, with a dense stand of a zingiberaceous plant along the roadside. The ants inhabited a loose-weave carton nest that enveloped several leaves in the clump of zingibers. I found a single colony queen in the center of the carton nest. Workers have been collected from low vegetation. Davidson has observed workers tending Homoptera and visiting extrafloral nectaries in Peru. (Longino 2003)

Identification
Longino (2003) - The very thin, almost needle-like propodeal spines uniquely identify this species. Additional characters are largely punctate face, amber dorsal setae, and erect tibial pilosity. The rugae on the face of the lectotype form a concentric pattern. Specimens from elsewhere are variable in the strength and orientation of face sculpture. The syntypes of the synonymized Crematogaster aruga are within the range of variation for arcuata, with facial rugae somewhat reduced relative to the average condition.

Distribution
Longino (2003) - Costa Rica to southern Brazil, Bolivia.

Distribution based on Regional Taxon Lists
Neotropical Region: Bolivia, Brazil, Colombia, Costa Rica, Panama, Panama , Peru, Venezuela.

Nomenclature

 *  arcuata. Crematogaster sulcata r. arcuata Forel, 1899c: 84, pl. 4, fig. 3 (w.) PANAMA. Longino, 2003a: 36 (q.). Combination in C. (Physocrema): Forel, 1913l: 234; in C. (Orthocrema): Emery, 1922e: 134; in C. (Neocrema): Santschi, 1922d: 244; Kempf, 1972a: 83. Raised to species: Forel, 1913l: 234. Senior synonym of aruga: Longino, 2003a: 35.
 * aruga. Crematogaster (Physocrema) arcuata var. aruga Forel, 1913l: 234 (w.) BRAZIL. Combination in C. (Orthocrema): Emery, 1922e: 134; in C. (Neocrema): Kempf, 1972a: 83. Junior synonym of arcuata: Longino, 2003a: 35.

Worker
Longino (2003) - HL 0.701, 0.629, 0.785; HW 0.772, 0.661, 0.867; HC 0.679, 0.600, 0.773; SL 0.776, 0.733, 0.860; EL 0.166, 0.147, 0.184; A11L 0.287; A11W 0.131; A10L 0.148; A10W 0.110; A09L 0.107; A09W 0.085; A08L 0.080; A08W 0.066; WL 0.880, 0.829, 0.948; SPL 0.187, 0.206, 0.302; PTH 0.201, 0.177, 0.224; PTL 0.289, 0.283, 0.330; PTW 0.228, 0.191, 0.253; PPL 0.187, 0.184, 0.212; PPW 0.285, 0.243, 0.285; CI 110, 105, 110; OI 24, 23, 23; SI 111, 117, 110; PTHI 70, 63, 68; PTWI 79, 67, 77; PPI 152, 132, 134; SPI 21, 25, 32; ACI 0.07.

Color dark red brown to black.

Head subquadrate, with compound eyes projecting beyond lateral margins in full face view; mandibles striate; clypeus emarginate anteriorly and often with anteromedian impression, convex, shiny, with widely spaced weak rugulae that are longitudinal to transversely arcing; face punctatorugose over much of surface, with variably developed anteromedian strip on face smooth and shiny; scapes with a combination of erect and subdecumbent setae, setae abundant, as long as width of scape or greater; antennal club not well defined, terminal 3-5 segments gradually lengthening and becoming increasingly densely pubescent, or in some cases relatively distinctly 3-segmented; face with abundant long erect amber to black setae, both on dorsal surface and projecting from sides, forming a black crown in full face view; malar spaces and ventral surface of head with abundant short erect to suberect setae.

In lateral view, dorsal profile of promesonotum low, weakly convex, mesonotum differentiated from pronotum, projecting and forming elevated anterior boss; propodeal suture broad, well impressed; mesonotum meeting dorsal face of propodeum at angle, dorsal and posterior faces of propodeum distinct; propodeum strongly swollen, large relative to promesonotum, nearly as wide as pronotum in dorsal view; propodeal spines thin, almost needle-like, of variable length but usually long; side of pronotum evenly punctate and medially impressed; katepisternum evenly punctate; anepisternum punctate to rugose; side of propodeum faintly microareolate to smooth and shining, always with much weaker sculpture than side of pronotum and katepisternum; promesonotal dorsum and dorsal face of propodeum punctatorugose; posterior face of propodeum smooth and shiny; promesonotum and dorsal face of propodeum with abundant long coarse black to amber setae, no setae on posterior face of propodeum; legs with combination of abundant suberect and decumbent setae.

Petiole in side view subtriangular, strongly to faintly punctate; anteroventral tooth weak to absent; dorsal face rectangular, longer than wide, smooth and shiny on anterior two thirds, faintly microaerolate on posterior third, with row of four coarse black setae across posterior margin; postpetiole with short ventral tooth, postpetiole in dorsal view subquadrate, wider than long, posterior margin emarginate, with weak to pronounced longitudinal median sulcus, and abundant long coarse black setae; fourth abdominal tergite with faint microareolate sculpture; fourth abdominal tergite with abundant erect coarse black setae.

Queen
Longino (2003) - (Venezuela) In lateral profile dorsal face of propodeum sloping obliquely from postscutellum, such that most of propodeum is posterior to scutellum (in contrast to normal queens, in which dorsal face of propodeum drops steeply from postscutellum and much of propodeum appears ventral to scutellum and postscutellum); face covered with widely-spaced clathrate rugae, interspaces shiny; pronotum similarly rugose anteriorly, grading to finer striae and dense punctation on sides; mesonotum longitudinally reticulate rugose; upper anepisternum longitudinally rugose striate, remainder of anepisternum and katepisternum smooth and shiny; dorsal and upper lateral face of propodeum rugose, posterior and lower lateral face smooth and shiny; propodeal spines distinct, sharp; petiole, postpetiole, and fourth abdominal tergite smooth and shining; dorsal face of petiole proportionally shorter than petiole of worker, only slightly longer than wide; abundant short amber to whitish erect setae on entire dorsum including face, mesosoma, petiole, postpetiole, and fourth abdominal tergite; size characters as in Figures.

Type Material
Longino (2003) - Syntype workers: Panama, Volcan de Chiriqui, 3-4000ft (Champion), (examined, MHNG worker here designated LECTOTYPE).