(Figs. 34, 35, 36)
Shape of head, propodeum, and petiole shown in figs. 34, 35, 36. Note the broad convex mandibles with cultrate masticatory margins, apex of mandible subtruncate viewed end on; masticatory margin rounding evenly into basal margin. Basidorsal groove very fine, indistinct, not reaching lateral margin. Clypeus gently concave in the middle and with free margin medially concave. Clypeus not distinctly delimited from the frontal lobes, but the frontal area forming a distinct pit that trails a shallow sulcus back to the center of the vertex. Eyes taking up approximately a third of length of sides of head, separated from antennal insertion by about 0.15 mm, or a little more than half the eye length. Undermouthparts closed, but palpi apparently with maxillary 6 and labial 4 segments (4 and 3 segments visible respectively); palpi short, in repose barely surpassing the posterior buccal border.
Antennae with pedicel very slightly longer than broad and very slightly longer than the succeeding (second funicular) segment; second segment very slightly broader than long; remaining funicular segments broader than long, except for apical segment.
Trunk robust, with a weakly convex dorsal profile as seen from side view, about 2 1 / 2 times as long as broad seen from above, with rounded humeri and steep sides of pronotum, but not really marginate dorsolaterally. Sides of pronotum with an impression in posterior part. Promesonotal suture distinct, impressed, apparently flexible; metanotal groove obsolete, marked by a feeble impression at sides of dorsum. Mesopleuron distinctly bounded by complete sutures above and behind. Propodeal declivity concave, bounded by distinct margins that are especially prominent at the upper corners, but weak in the upper-middle portion due to a feeble median posterior impression of the dorsal face, seen best in oblique light. Upper part of declivity shining, very finely punctulate; lower part coarsely, transversely striate. Femur of anterior leg strongly incrassate — almost as strongly as in P. angusta .
Node well shown in figs. 34 and 35; note the lack of posterolateral teeth or angles and the faint vestige of a median tooth. Subpetiolar process rounded ventrally, with a small notch behind. Gaster with first 2 segments (postpetiole and true abdominal segment IV) about equal in width, with the second segment a little longer than the first, constriction between them moderately distinct. Sting robust, compressed.
Sculpture of the usual opaque kind in Platythyrea , very finely and densely reticulate with fine, overlying pruinosity, the reticulation becoming more transversely elongate on gaster, and slightly more shining here. Coarse punctures abundant on vertex mesad of and behind eyes, but rather weak and inconspicuous. Coarser punctures on sides and posterior dorsum of trunk, on petiolar node, especially sides and anterior dorsum, and on dorsum of postpetiole. Fine, short erect hairs on mandibles, anterior clypeal margin, and gastric apex.
Color black; mandibles, antennae, and tarsi brownish yellow; tibiae and gastric apex dull yellowish brown; femora brown.
Holotype a worker from Ecuador: 2 - 8 miles N of Puyo, Pastaza (or Napo), about 950 m, 9 February 1955 (E. I. Schlinger and E. S. Ross), deposited in CAS — San Francisco.
This species is distinguished from all New World Platythyrea except P. exigua by its very small size. It differs from exigua by its much shorter head and virtually unarmed petiolar node. The node is also different in shape from those of all other neotropical species. The anterior femur is broadened almost as much as in P. sinuata , and the basidorsal groove of the mandible is present, though very fine. The type locality is in western Amazonian forest with small clearings, just out of sight of the Andes to the west (notes from E. S. Ross).
Figures 7 - 10. Two new species of Probolomyrmex , holotype workers, both from S India, petiole and adjacent structures in side view (7, 8) and dorsal view (9, 10), X 73.
