Crematogaster rifelna

I found this species in old cynipid oak galls and in twigs and small branches of oaks and various trees in the several localities from Victoria to Brownsville, Texas. Colonies with winged females and males were found September 23 and 24, 1942. (Buren 1968)

Identification
Buren (1968) - C. rifelna is very distinct from other North American species in the possession of the median impression on the pronotum. In appearance and its arboreal habits it resembles Crematogaster ashmeadi, but such resemblances are probably due to convergence rather than any close relationship. The male of rifelna, as in Crematogaster coarctata (as californica), lacks the lateral impressions on the scutellum, an important and constant character throughout the lineolata-laeviuscula and sanguinea-ashmeadi groups. This character alone, without the pronotal impression of the worker, would serve to separate rifelna from these groups.

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

Nomenclature

 *  rifelna. Crematogaster (Crematogaster) rifelna Buren, 1968b: 96 (w.q.m.) U.S.A.

Worker
Length about 3 to 3.6 mm.

Head, excluding mandibles, a little broader than long, with convex sides and posterior border straight or slightly excised in the middle. Scapes not reaching posterior corners in largest workers, barely surpassing them in small specimens. Humeri of pronotum strong and marked by rugae. Mesonotal carina strong and sharp, especially in front. Anterior to this carina on the pronotum is a distinct, rather smooth, median impression. Thus when the pronotum is viewed in front, the sharp mesonotal carina may be seen through this impression almost like a gun sight. Promesonotum somewhat flattened above in profile. Mesonotal declivity present but strongly angled. Epinotal spines straight, short, a little shorter than interbasal distance, parallel or feebly diverging, directed somewhat upward as well as backward, often with a little impression on base of epinotum just before base of each spine. Petiole with rounded sides seen from above. Hemilobes of postpetiole broad and rounded.

Genal striae very fine and closely set but distinctly etched and carried well past the eyes. Front and all of the rear of the head smooth and shining. Front and dorsum of pronotum irregularly rugose on the sides, finely striato-punctate toward the middle and the median impression usually shining. Sides of pronotum finely striato-punctate, smooth in the oblique impressions. Mesonotum finely striato-punctate. Mesopleura punctate. Metapleura mostly punctate below, striate above. Base of epinotum with strong, straight longitudinal striae, declivity smooth and shining. Postpetiole with faint, fine punctures.

Pubescence rather long, appressed on all parts but scapes, there suberect. Erect hairs not fine, several present on shoulders of pronotum and a few also at rear of mesonotum; on gaster confined mostly to the usual rows near posterior borders of the segments.

Queen
Length about 7 mm.

Head, excluding mandibles, broader than long, somewhat broader •behind than in front, with convex sides and straight or slightly excised posterior border. Scapes far short of reaching hind corners, reaching only to about level of lateral ocelli. Ocelli small. Head much broader than thorax. Mesoscutum a little longer than broad. Scutellum wider than long. Epinotal spines very short, less in length than diameter of their bases. Postpetiole with distinct if feeble impression for its entire length; without spiracular angles.

Clypeus distinctly convex in the middle, all densely striate; no median shining streak. Genae very densely striate (7 striae per 0.1 mm.), this sculpture carried well past the eyes. Rest of head smooth and shining. Pronotum finely punctate, smooth only at rear. Mesosternal sides striato-punctate, mesopleura with a few striae or smooth and shining. Metapleura striate and with fine intercalated punctures. Sides of epinotum striate. Base of epinotum with long longitudinal striae and rugae. Sides of petiole finely punctate. Postpetiole smooth and shining above.

Pubescence short and appressed on all parts. Erect hairs rather sparse on all parts.

Concolorously black. Wing veins and stigma brown.

Concolorously black.

Male
Length about 3 mm.

Basal funicular joints slightly broader than long. Head rather elongate and with very convex posterior border. Ocelli small, the vertex at rear border of head. Thorax a little broader than head. Mesoscutum a little broader than long. Scutellum without trace of lateral impressions, shaped, therefore, as in the female.

Head weakly punctate, shining. Mesoscutum finely striate, shining only on front of parapsides. Pronotum shagreened, subshining, smooth at rear. Mesosternal sides weakly striato-punctate, mesopleura striate in an oblique streak. Metapleura weakly striato-punctate. Sides of epinotum shallowly punctate. Base of epinotum smooth and shining. Pubescent hairs short, suberect on head and thorax, appressed on gaster. Only a few erect hairs present.

Concolorously black. Wing veins very pale yellow.

Type Material
Riviera, Texas.

Holotype worker, 45 paratype workers, ten paratype females, and four paratype males from a few miles south of Riviera, Texas-W. F. Buren, collector. Included in the paratype series also are numerous workers, females, and males from several series from Victoria, Barroso, Riviera, Harlingen, and Brownsville, Texas. Also seen were a series collected at Victoria, Texas by J. D. Mitchell, a series in the collection of the Museum of Comparative Zoology from Mirador, Mexico, nesting in Tillansia streptophylla, and specimens from Gambel Creek, Tex. and Valles, S. L. Potosi, and Ciudad Victoria, Tamaulipas, Mex.- Wm. S. Creighton, collector.

Since numerous type specimens are at hand, they will be distributed among the various museums so as to be of readily available reference use. The holotype and a number of paratypes will be deposited in the National Museum. Other paratypes will go to the Museum of Comparative Zoology, American Museum of Natural History, and California Academy of Sciences.

Etymology
The name is derived from the old low German “rifeln”- to furrow.

References based on Global Ant Biodiversity Informatics

 * Dattilo W. et al. 2019. MEXICO ANTS: incidence and abundance along the Nearctic-Neotropical interface. Ecology https://doi.org/10.1002/ecy.2944
 * Kempf, W.W. 1972. Catalago abreviado das formigas da regiao Neotropical (Hym. Formicidae) Studia Entomologica 15(1-4).
 * Morgan C., and W. P. Mackay. 2017. The North America acrobat ants of the hyperdiverse genus Crematogaster. Mauritius: LAP LAMBERT Academic Publishing, 540 pp.
 * O'Keefe S. T., J. L. Cook, T. Dudek, D. F. Wunneburger, M. D. Guzman, R. N. Coulson, and S. B. Vinson. 2000. The Distribution of Texas Ants. The Southwestern Entomologist 22: 1-92.
 * Vásquez-Bolaños M. 2011. Lista de especies de hormigas (Hymenoptera: Formicidae) para México. Dugesiana 18: 95-133
 * Wheeler, G.C. and J. Wheeler. 1985. A checklist of Texas ants. Prairie Naturalist 17:49-64.