Thaumatomyrmex atrox, Weber, N. A., 1939

Weber, N. A., 1939, New ants of rare genera and a new genus of ponerine ants., Annals of the Entomological Society of America 32, pp. 91-104 : 98-99

Thaumatomyrmex atrox , sp. nov.

(Fig. 3)

Worker.-Length about 4.4 mm. Head, between anterior clypeal margin and occiput, three-fourths as long as wide between outer margins of eyes; anterior and posterior clypeal margins convex; sides of head distinctly converging back of eyes; posterior margin concave, occipital corners smoothly rounded. Mandibles with three long, acute teeth and a rudimentary basal fourth in the form of a flattened, acute tubercle. Antennal scapes curved, distinctly exceeding occiput. Thorax from above with sides of pronotum distinctly more convex and broader than rest of thorax. Petiole from above much broader behind, with transverse posterior margin and sides converging in slight convexity to concave anterior margin. Gaster large, with truncate anterior margin. Legs moderately long and slender.

Body smooth and shining except for fine, short vermiculate impressions resembling a very sparse, appressed pubescence.

Pilosity of very sparse, obtuse and coarse reclinate hairs, most numerous and backwardly directed on gaster, shorter and appressed on appendages, becoming a finer pubescence on antennal tips.

Color shining black with pale brown appendages, including mandibles.

Described from one worker (holotype) taken by myself on Kartabo Point, at the junction of the Mazaruni and Cuyuni Rivers, British Guiana, August 20, 1935, and one worker (metatype) taken by myself in the foothills north of Tunapuna, Trinidad, B. W. I., July 29, 1935. Intensive collecting in both localities failed to reveal other workers and testifies to the extreme rarity of these archaic ants. Both specimens were among leaves and, as there were no land snails in either place, a snail-eating habit could not be inferred (cf. Creighton, 1928). It is more probable that the bizarre mandibles are used for capturing other Arthropods (cf. the myriapod-eating habit of Emeryella schmitti discovered by Dr. Mann (Wheeler and Mann, 1914). Similar bizarre mandibles are common in Strumigenys and I have found a Strumigenys worker carrying a collembolan ( Entomobrya sp.), controvening a theory that the ants of this genus fed on fungi.

Of the previously known three species this new species is closest to T. ferox discovered by Dr. W. M. Mann in Honduras. It is larger than cochlearis or mutilatus and smaller than ferox . From cochlearis it differs further in lacking punctate sculpturing on body and fine ridges radiating back from clypeus, in proportions of thorax and petiole, in more anteriorly diverging head, and in mandibular teeth proportions. A cotype of ferox differs from this new species in having the pronotum more convex laterally, in having an even convexity between the pro- and mesonotum, in having the petiole more bi-convex and less plano-convex when viewed laterally, in having distinctly thicker petiole apex, in having a shorter head and in mandibular teeth proportions. Sculpturing and pilosity are similar.

Dr. W. M. Mann kindly allows me to describe a fifth species which he took at Huachi Beni, Bolivia: