Myrmelachista guyanensis

Wheeler (1934) collected the types from "tenuous, anastomosing galleries in dead twigs and branches."

Identification
Worker with nine antennal segments. See Longino's comments regarding Myrmelachista of South America.

Distribution based on Regional Taxon Lists
Neotropical Region: Bolivia, Brazil, French Guiana, Guyana, Suriname.

Nomenclature

 *  guyanensis. Myrmelachista guyanensis Wheeler, W.M. 1934g: 198 (w.q.) GUYANA.

Worker
Length 1.3-2 mm.

Head subrectangular, rather flat, slightly longer than broad and slightly narrower in front than behind, with feebly concave posterior and feebly convex lateral borders. Eyes small, flat, slightly in front of the middle of the sides. Mandibles stout, convex, 5-toothed, the median tooth minute. Clypeus convex in the middle, its anterior border sinuate on each side, rounded, projecting and crenulate in the middle and sometimes bearing two closely approximated denticles in the position of the single denticle of other species. Frontal area rather distinct, flat and triangular. Antennae short; scapes curved and somewhat flattened at the base, extending about twice their greatest diameter beyond the posterior orbits; joints 2-5 of the funiculus subequal, strongly transverse, two basal joints of club subequal, together somewhat shorter than the terminal joint. Thorax of the usual shape but rather depressed above; mesoepinotal constriction short and rather feeble in profile, deep on the sides; metaepinotal suture distinct but the metanotal spiracles not projecting; base of epinotum flattened, straight in profile, longer than the very sloping declivity. Petiole with distinct posterior peduncle; scale slightly inclined forward, narrow below, widening above, with slightly convex sides and feebly but distinctly excised, though blunt superior border, so that in profile it is nearly as thick above as below.

Very smooth and shining, minutely and sparsely punctate; mandibles finely punctate-reticulate at the tips; metanotum more opaque, reticulate-rugulose.

Erect hairs and pubescence pale, whitish; the former very scarce, confined to the clypeus and posterior borders of the gastric segments; the latter sparse, appressed, moderately long on the head, thorax and gaster, very short and dilute on the legs and antennae.

Castaneous brown; thorax alone or both head and thorax sometimes paler and more reddish brown; cheeks and clypeus yellowish brown; mandibles, antennae, tibiae, articulations of legs, sutures of thorax and posterior borders of gastric segments brownish yellow; mandibular teeth black; antennal clubs slightly darker than the bases of the funiculi but not infuscated.

Queen
Length 3-3.3 mm.

Head like that of the worker in being distinctly narrower anteriorly, but suboblong, one and one-fourth times as long as broad, with straight sides and posterior border. Eyes larger, flat, placed more anteriorly; ocelli small, widely separated. Anterior clypeal border broader, less projecting and more nearly straight, crenulate or with two minute, closely approximated median denticles. Thorax broader than the head, twice as long as broad, much flattened, especially in the region of the mesonotum, which is large, subhexagonal, as broad as long; epinotum low, its dorsal surface very feebly convex, sloping, without distinct base and declivity. Petiolar scale thicker, stouter, with entire, much more obtuse superior border than in the worker. Gaster elongate-elliptical, as long as the remainder of the body. Wings long, with one long cubital cell and no discoidal cell.

Sculpture, pilosity and color as in the worker, but the mesonotum and scutellum pale brown or brownish yellow. Wings colorless, with pale yellow veins and pterostigma.

Type Material
Described from numerous workers and five females which I took at Kartabo, British Guiana, inhabiting tenuous, anastomosing galleries in dead twigs and branches.

Longino (2006) - Syntype workers, queens:,  (USNM syntype worker examined).

References based on Global Ant Biodiversity Informatics

 * Fernández, F. and S. Sendoya. 2004. Lista de las hormigas neotropicales. Biota Colombiana Volume 5, Number 1.
 * Franco W., N. Ladino, J. H. C. Delabie, A. Dejean, J. Orivel, M. Fichaux, S. Groc, M. Leponce, and R. M. Feitosa. 2019. First checklist of the ants (Hymenoptera: Formicidae) of French Guiana. Zootaxa 4674(5): 509-543.
 * Kempf W. W. 1978. A preliminary zoogeographical analysis of a regional ant fauna in Latin America. 114. Studia Entomologica 20: 43-62.
 * Kempf, W.W. 1972. Catalago abreviado das formigas da regiao Neotropical (Hym. Formicidae) Studia Entomologica 15(1-4).
 * Ulyssea M. A., L. Pires do Prado, C. R. F. Brandao. 2017. Catalogue of the Dolichoderinae, Formicinae and Martialinae (Hymenoptera: Formicidae) types deposited at the Museu de Zoologia da Universidade de Sao Paulo, Brazil. Papeis Avulsos de Zoologia 57(23): 295-311.
 * Ulyssea M. A., L. Pires do Prado, and C. R. F. Brandao. 2017. Catalogue of the Dolichoderinae, Formicinae and Martialinae (Hymenoptera: Formicidae) types deposited at the Museu de Zoologia da Universidade de Sao Paulo, Brazil. Papeis Avulos de Zoologia 57(23): 295-311.
 * Wheeler W. M. 1934. Neotropical ants collected by Dr. Elisabeth Skwarra and others. Bulletin of the Museum of Comparative Zoology 77: 157-240.