Trachymyrmex guianensis, Neal A. Weber, University of North Dakota, 1936

Neal A. Weber, University of North Dakota, 1936, The biology of the fungus-growing ants. Part. I. New forms. 1, Revista de Entomologia 7, pp. 378-409 : 404-405

Trachymyrmex guianensis , sp. nov.

Worker: Length 3.6 mm. - Head, excluding mandibles, as broad as wide, broadly impressed on posterior margin, occipital angles with a low, rounded spine densely covered with slender, acute tubercles. Lateral margins irregularly convex; viewed from in front, a bifurcate tubercle projects below the occipital spine and the margins project slightly beyond the eyes, which are moderately convex and situated in front of the middle. Anterior clypeal margin convex, broadly notched in middle; posterior margin raised laterally in front of the frontal lobes as a high, acute crest. Frontal lobes rounded posteriorly, acutely angular tin front. Antennal scapes sub-cylindrical, slightly curved and smaller in diameter at basal 1/4, exceeding occipital angles by a distance less than their distal diameter. Terminal joint of funiculus slightly longer than the adjacent joints 7-9 taken together and slightly shorter than joints 2-5 taken together.

Lateral pronotal spines large, straight and acute, directed anteriorly and laterally. In front of these a dorso-lateral carina extends to the anterior margin; a slight carina extends downward from this point for a very short distance and another irregular and tuberculate carina extends over the dorsal surface to the other side, the junction of the three carinae being raised. Between the lateral pronotal spines are two distinct and bifurcate median tubercles and a lateral tubercle at the base of the spines. Inferior pronotal spines large, straight and stout. Mesonotum, in profile, with an anterior raised tuberculate convexity and a posterior tuberculate convexity prolonged apically in laterally compressed, truncate spine. Basal surface of epinotum without carinae, bearing a discontinuous row of small tubercles on either side. Epinotal spines long, slender, and acute.

Petiole, from above, slightly over 1/2 as wide as postpetiole. Dorsal surface of epinotum bearing four small tubercles. Dorsal surface of postpetiole with numerous sub-equal tubercles. Gaster densely and coarsely tuberculate, marginate on sides, tubercles on sides and posteriorly partly fused.

Opaque; with abundant fine whitish papillae and a grayish bloom. - Pilosity of sparse, coarse, and black hairs prising from the tubercles of body and mostly recurved, - Ferruginous with gaster brown and appendages lighter.

Described from one worker taken by myself July 17, 1938, on an island near the outlet of the New River, main tributary of the Courantyne River, British Guiana.

This species is close to T. urichi Forel from which it differs chiefly in having carinae on sides of clypeus, angular anterior margin of frontal lobes, stouter, shorter, and more coarsely tuberculate antennal scapes, in having distinct carinae in front of pronotal spines, and in lacking the distinct anterior mesonotal spine.