Octostruma pexidorsum

The type series is from lowland Amazonian rainforest, in a Berlese sample of forest floor litter.

Identification
Longino (2013) - Face lacking transverse arcuate carina; basal five teeth of mandible acute; labrum longer than wide, sides nearly parallel, apex bluntly rounded, not bilobed; face densely punctate; ground pilosity of face, dorsal promesonotum, and first gastral tergite conspicuous, composed of thin, yellow, suberect and strongly curved setae, giving dorsum a scruffy or wooly appearance; pair of long filiform setae projecting from petiolar peduncle anterior to spiracle, shorter filiform setae projecting from sides of postpetiole and anteromedian first gastral sternite (these filiform setae otherwise only known in Octostruma iheringi).

Key to Octostruma workers

Distribution based on Regional Taxon Lists
Neotropical Region: Colombia.

Castes
Known only from the worker caste.

Nomenclature

 *  pexidorsum. Octostruma pexidorsum Longino, 2013: 47, figs. 11, 34, 44 (w.) COLOMBIA.

Worker
HW 0.63–0.71, HL 0.59–0.65, WL 0.66–0.74, CI 107–111 (n=3). Labrum longer than wide, sides nearly parallel, apex bluntly rounded, not bilobed; mandible triangular, in profile view with mandible closed, in same plane as clypeus, apex of mandible not down-turned; with mandible fully open, dorsal face remains in same plane as clypeus; mandible with 8 teeth, tooth 1 continuous with basal rim of dorsal surface, all teeth acute; tooth 1 smaller than teeth 2–5 and 8, teeth 5–8 forming an apical fork, with 5 and 8 large, 6 and 7 small partially confluent denticles; on one specimen with spread mandibles, a minute denticle between teeth 3 and 4; dorsal surface of mandible roughened; ventral surface flat and parallel to clypeus apically, twisting basally to nearly perpendicular orientation basally, smooth and shining; interior surface concave, smooth and shining; scape flattened, with pronounced anterobasal lobe, dorsal surface minutely densely punctate; clypeus with broad, shallow emargination anteriorly; clypeus and anterior face roughened and dull, grading to densely punctate on medial and posterior face; frontal carinae faint, nearly obsolete; antennal socket deep, dorsal rim of socket continuous with pronounced dorsal margin of antennal scrobe; antennal scrobe deep, strongly delimited dorsally, posteriorly, and ventrally with sharply defined thin cuticular rim; compound eye small, circular, composed of about 7 ommatidia; distinct carina extends from ventral margin of antennal socket across floor of scrobe to compound eye; scrobe floor faintly foveolate; occipital carina short, not extending anterior to occipital foramen; undersurface of head punctate. Mesosomal dorsum evenly convex in profile, promesonotal suture and metanotal groove not impressed; propodeum with distinct dorsal and posterior faces; propodeal spines well-developed, in the form of acute, laterally flattened plates, inner surface concave; a few transverse rugulae between propodeal spines; propodeal spiracle large, filling space between ventral margin of propodeal spine and metapleural lobe, extending posteriorly to form posterior margin of propodeum; entire pronotum, mesonotum, and dorsal face of propodeum densely punctate; mesopleuron and side of propodeum confluent, dorsal portion punctate, ventral portion smooth, matte; posterior face of propodeum faintly foveolate and sublucid.

Petiole in profile with peduncle differentiated from node, node with differentiated anterior face, posterodorsal face sloping to acute posterior rim; anteroventral margin with pronounced, anteriorly-directed peg-like tooth; postpetiole low, broad, crescent-shaped in dorsal view; dorsum of petiolar node and postpetiole densely punctate; first gastral tergite and sternite densely punctate, puncta of sternite larger and more widely spaced than puncta of tergite.

Anterior labral lobe with radiating tuft of soft, thick, translucent, capitate setae of unequal length projecting from apex; each larger mandibular tooth with fully appressed seta running length of tooth; anterior margin of scape with about 7 stiff slightly clavate setae, seta on basal lobe longest, no seta proximal to this longest seta; ground pilosity of face, dorsal promesonotum, and first gastral tergite conspicuous, composed of thin, yellow, suberect and strongly curved setae, giving dorsum a scruffy or wooly appearance; face with 2–6 long, thin, stiff, erect setae, posteromedian pair always present, other variably distributed on lateral and posterolateral margins; mesonotum and petiolar node each with a pair of stiff, weakly clavate setae; apex of mesotibia with 2 stiff setae; postpetiole with 0–2 weakly clavate setae; first gastral tergite with 8–14 erect weakly clavate setae; first gastral sternite with abundant short stiff setae; pair of long filiform setae projecting from petiolar peduncle anterior to spiracle, shorter filiform setae projecting from sides of postpetiole and anteromedian first gastral sternite; ground pilosity of first gastral tergite sparse, seta length less than distance between them.

Color dark brown.

Type Material
Holotype worker: COLOMBIA, Amazonas: 7 km N Leticia [-4.1466, -69.9343, unknown error], 75 m, 10 Feb 1972, forest, leaf litter (S. & J. Peck, B-230), unique specimen identifier MCZ-ENT00511319. Paratype workers: same data, MCZ-ENT00511314; , MCZ-ENT00511315; , MCZ-ENT00511316; MCZC, MCZ-ENT00511317, MCZ-ENT00511318, MCZ-ENT00511320, MCZ-ENT00511321, MCZ-ENT00511322.

Etymology
The name refers to the wooly ground pilosity. It is a noun in apposition and thus invariant.