Stenamma monstrosum

Stenamma monstrosum is a rare species known from only three collections of sifted leaf litter taken from the forest floor. It occurs in montane wet forest (e.g. cloud forest, mixed hardwood forest) and has been recorded from 1400–1650 m elevation. Because of its rarity in leaf litter, and its gracile phenotype, I hypothesize that S. monstrosum is arboreal. (Branstetter 2013)

Identification
Branstetter (2013) - Integument mostly mottled brown to red-brown or orange-brown; medium-sized species (see HL, ML, PrW below); basal margin of mandible with a deep proximal notch containing a small tooth; anterior clypeal margin with a deep unevenly rounded depression that, when viewed from an anterodorsal angle, has two distinct outer teeth and two indistinct inner teeth (all pointing ventrally); mesosoma profile appearing elongate, almost gracile; metanotal grove relatively wide and shallow, not well demarcated by the promesonotal and propodeal margins; propodeal dorsum elongate, distinctly longer than propodeal declivity; gastral pilosity clearly bilayered, with a layer of long suberect setae and a layer of short subdecumbent setae; eye relatively small (EL 0.09–0.11, REL 13–15), with 5–6 ommatidia at greatest diameter; scape and metafemur relatively long (SI 104–120, MFI 70–80); frontal lobes well-developed (FLD 0.16–0.19, FLI 23–25), but not completely covering torular lobes in full-face view; 4-segmented antennal club very distinct.

Similar to Stenamma manni, Stenamma saenzae but the shallow metanotal groove, deeply emarginate clypeus and the tooth in the basal margin of the mandible will easily separate ''S. monstrosum from any other species.

Distribution
Honduras to Nicaragua.

Distribution based on Regional Taxon Lists
Neotropical Region: Honduras, Nicaragua.

Castes
Known only from the worker caste.

Nomenclature

 *  monstrosum. Stenamma monstrosum Branstetter, 2013: 187, figs. 123, 124 (w.) HONDURAS.

Description
(5 measured) HL 0.79–0.94 (0.91), HW 0.63–0.82 (0.78), FLD 0.16–0.19 (0.17), PCW 0.03–0.03 (0.03), SL 0.76–0.86 (0.83), EL 0.09–0.11 (0.11), ACL 0.75–0.80 (0.78), ML 1.03–1.21 (1.15), PrW 0.46–0.55 (0.52), PSL 0.12–0.15 (0.15), SDL 0.11–0.12 (0.11), PL 0.38–0.42 (0.42), PH 0.19–0.23 (0.23), PW 0.14–0.17 (0.15), PPL 0.19–0.20 (0.20), PPH 0.17–0.21 (0.20), PPW 0.18–0.22 (0.21), MFL 0.90–1.03 (1.10), MTL 0.71–0.83 (0.82), CI 80–87 (85), SI 104–120 (107), REL 13–15 (14), FLI 23–25 (23), PSI 1.1–1.3 (1.3), MFI 70–80 (77), ACI1 62–64 (63), ACI2 93–98 (95).

Medium-sized species; general body color a mottled brown to red-brown or orange-brown, with patches of yellow-brown, especially on gaster; appendages generally lighter, orange-brown to yellow-brown; setae golden brown; mandible with 2–3 distinct apical teeth, 1–2 distinct basal teeth, and a variable number of almost imperceptible denticles in between (usually appearing as a long, flat diastema), basal tooth well-defined and robust; basal margin of mandible with a very deep proximal notch containing a small tooth; mandible mostly smooth and shiny, with scattered piligerous punctae and a variable number of striae; anterior clypeal margin with a deep unevenly rounded depression, that, when viewed anteriorly, has two distinct outer teeth and two indistinct inner teeth (all pointing ventrally); median lobe of clypeus somewhat obliquely flattened and concave, without a pair of longitudinal carinulae, only sometimes with a short transverse carinula before anterior margin, remainder of clypeus mostly smooth and shining; posterior extension of clypeus between antennal insertions somewhat narrow (PCW 0.03), sides subparallel; frontal lobes well-developed (FLD 0.16–0.19, FLI 23–25), but not completely covering torular lobes in full-face view; head elongate and roughly oval-shaped (CI 80–87), with posterior margin depressed medially; eye relatively small (EL 0.09–0.11, REL 13–15), subcircular to oval-shaped, with 5–6 ommatidia at greatest diameter; face densely rugoreticulate, with a few longitudinal rugulae medially, interstices with faint piligerous punctae; scape relatively long (SI 104–120), surpassing posterior margin of head when laid back; scape cuticle mostly smooth and shiny, with scattered piligerous punctae and fine striations; flagellum with a very distinct 4-segmented antennal club; mesosoma densely sculptured, promesonotal dorsum mostly with longitudinal rugae and rugoreticulae, but a few transverse rugulae present around anterior declivity; lateral side of mesosoma with irregular rugulae and punctae; propodeal declivity mostly smooth and shining, sometimes with faint transverse striae; promesonotum in profile low-domed and slightly asymmetrical, with the apex occurring anterior of the midpoint, anterior face more strongly defined and longer than posterior face; metanotal grove relatively wide and shallow, not well demarcated by the promesonotal and propodeal margins; propodeal dorsum elongate, distinctly longer than propodeal declivity; mesosomal outline in profile appearing elongate, almost gracile; propodeal spines forming sharp tubercles (PSL 0.12–0.15, PSI 1.1–1.3); petiole somewhat elongate and gracile (PL/HW 0.51–0.60), node small (PH/PL 0.53–0.56), with a long sloping anterior face, and a short vertical posterior face, dorsal surface in profile view rounded, pointing vertically; postpetiolar node slightly smaller than petiolar node (PPH/PH 0.90–0.97), anterior face longer and more sloping angled than posterior face; petiole and postpetiole mostly punctate, with anterior face of postpetiolar node largely smooth and shiny; gaster mostly smooth and shiny, with scattered piligerous punctae; much of body with long suberect to sub-decumbent pilosity; scapes with mostly subdecumbent setae; gastral pilosity somewhat sparse and clearly bilayered, with a layer of long suberect setae and a layer of short subdecumbent setae; setae on legs mostly subdecumbent to appressed, with suberect setae on ventral surface of profemur.

Type Material
Holotype worker. HONDURAS: Olancho, Parque Nacional La Mural-la, 15.09537°N, 86.73887°W ±20m, 1420m, 2 May 2010, cloud forest, ex sifted leaf litter (LLAMA, collection Wa-C-01-2-06) USNM, specimen CASENT0621327. Paratypes: same data as holotype 1w, EAPZ, CASENT0621329, 1w, MGBPC, CASENT0621330, 1w, MCZ, CASENT0621328, 1w, UCDC, CASENT0621326.

Etymology
The specific epithet monstrosum is in reference to the hybrid, Frankenstein-like form of this species.

References based on Global Ant Biodiversity Informatics

 * Branstetter M.G. 2013. Revision of the Middle American clade of the ant genus Stenamma Westwood (Hymenoptera, Formicidae, Myrmicinae). ZooKeys 295: 1277
 * Longino J. T. L., and M. G. Branstetter. 2018. The truncated bell: an enigmatic but pervasive elevational diversity pattern in Middle American ants. Ecography 41: 1-12.