Trachymyrmex phippsi, 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 : 405-407

Trachymyrmex phippsi , sp. nov.

Worker: Length 3.5-4.1 mm. - Head, excluding mandibles, 0.9 as long as broad, sides nearly straight and diverging posteriorly, posterior margin broadly impressed in middle. Eyes moderately convex, situated in front of middle of head. Tubercle on sides of head between occipital corners and eyes reduced to a slight roughened convexity. Occipital spine large.and stout, somewhat truncate and bearing several tubercles at apex. Frontal carinae low and of irregular height. Antennal scapes slightly curved, inflated at distal 2/5, exceeding occipital corners by a distance equal to nearly 3 1/2 their distal diameter. Terminal joint of funiculus distinctly shorter than joints 7-9 taken together and of nearly the same length as joints 2-4 taken together.

Lateral pronotal spines of thorax the largest spines of body, acute, directed forward and laterally; between these are two median and acute tubercles of irregular shape. Inferior pronotal lateral spines in the form of flat, rounded lamellae curved backward; ventral margins of pronotal pleurae extended downward similarly in flattened lamellae. Anterior spines of mesonotum with massive bases and irregular truncate and tuberculate apices; posterior pair of mesonotal spines less massive at the base, bituberculate. Posterior sloping surface of mesonotum on each side with an acute tubercle. Mesoepinotal impression broad and rounded. Basal surface of epinotum with a pair of anterior irregular spines, sometimes tuberculate, and the usual epinotal spines. These latter are acute, slender and subcylindrical over more than the distal 1/2.

Anterior surface of petiole nearly plane, prolonged dorsally as a pair of elongated, acute, and slender spines which overarch the dorsal surface. Postpetiole above with a row of irregular, acute tubercles on each side terminating posteriorly in low, tuberculate spines. Gaster with strongly tuberculate: lateral ridges. Legs moderately long and slender.

Opaque; finely shagreened. - Pilosity of pale yellowish., appressed hairs which are abundant but not obscuring integument because of small size. These hairs arising from tubercles are recurved. - Ferruginous. Median spot just above antennal insertions, a median spot on frons, and dorsal median, streak on gaster brown. Margins of mandibles and clypeus dark brown.

Female: Length 4.7-5.1 mm. - Resembling the worker closely, with similar occipital spines, inferior pronotal spines in the form of flattened, rounded, and curved lamellae, and long, acute epinotal spines. Lateral spines of pronotum long, acute, and stout at the base, curved forward and laterally, - Ferruginous with darker blotches as in the worker and median and parapsidal brown patches on scutum of mesonotum. First gastric segment infuscated on the margins and with a hastateshaped brown spot on dorsal surface. Wings irregularly infuscated, veins light brown.

Male: Length 3.3-3.5 mm. - Head, excluding mandibles, 0.9 as long as distance between outside margins of eyes. Lateral margins of head in front of eyes concave, back of eyes convex. Occipital corners with acute tubercles. Posterior margin broad and flat. Eyes very convex, as large in diameter as the distance from them to occipital corners. Anterior margin of clypeus nearly straight. Terminal joint of funiculus slightly shorter than joints 10-12 taken together and as long as joints 2-6 taken together.

Pronotum with distinct, straight, lateral spine, inferior angles spinose. Scutum of mesonotum in profile almost hemispherical, overarching pronotum. Epinotal spines slender and acute. Distinct paired dorsal spines on petiole and postpetiole, Dorsal surface of gaster tuberculate.

Opaque; distinctly and finely reticulate, posterior side of head more coarsely reticulate, parts of integument finely rugulose. - Short, pale yellowish hairs sparsely distributed over body, appressed on flat surfaces, recurved where arising: from tubercles. - Dark brown, mandibles and appendages lighter. Wings lightly infuscated, veins light brown.

Described from a colony taken by myself July 30, 1936, by the Oronoque River of the Courantyne River basin in about Latitude 2°42" North, British Guiana.

The nest of the ants was 165 cm. above ground, in the rotted branch of an old tree trunk which had fallen into neighboring, trees and was in an oblique position. The fungus garden was suspended from the roof of a cavity in the rotted wood and was attached at the sides and bottom. The nest will be described more fully in a subsequent paper.

This species is related to T. phaleratus Wheeler from which it differs chiefly in larger size, more angular frontal lobes, longer antennal scapes, more flattened and backwardly directed inferior pronotal spines, and in appressed pilosity. The male of phaleratus (undescribed) is much smaller, has the anterior clypeal margin distinctly notched, lacks the distinct pair of dorsal spines on petiole, has a more rugulose integument and is in other ways different.

Two dealate females taken in the same locality July 25 and July 30 may be considered topotype females. The female of July 25 was taken from beneath a mass of humus and debris on a rotted log on the ground. The female of July 29 was taken from a similar situation on another rotted log. In neither case was a fungus garden seen and they were evidently just starting to found their colonies, independently, after their marriage flight.

This species is dedicated to Major J. F. P h i p p s, Royal Engineers, now engaged in surveying one of the British Empire's most inaccessible and least known boundaries.