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This species belongs to the Middle American clade of Stenamma (see Branstetter 2012). All content on this page modified from Branstetter (2013) unless noted otherwise.// Distribution
Honduras. Known only from the type locality.
Stenamma atribellum is a cloud forest specialist ranging from 1550–2030 m elevation. It is known from one leaf litter sample and one nest collection. The nest was collected underneath the bark of a large log in cloud forest near the edge of dwarf forest. The entire nest was not censused, but it was relatively large, with at least 100 workers, a single queen and brood.
Worker diagnosis. Integument mostly black; medium- to large-sized species (see HL, ML, PrW below); gaster with elongate anterior constriction; entire body almost completely smooth and shiny, with only some faint carinulae and punctae; anterior clypeal margin with a median emargination; basal margin of mandible straight, without a basal notch or deep depression; eye relatively large (EL 0.16–0.20, REL 21–24), oval-shaped, with 9–10 ommatidia at greatest diameter; propodeal spines reduced to very small tubercles (PSL 0.10–0.13, PSI 0.9–1.0); gastral pilosity forming a layer of somewhat stout suberect setae, and a very sparse layer of short decumbent setae; frontal lobes of moderate width (FLD 0.19–0.22, FLI 24–26), not completely obscuring to- rular lobes in full-face view.
Worker description. (10 measured) HL 0.88–0.99 (0.94), HW 0.77–0.88 (0.86), FLD 0.19–0.22 (0.22), PCW 0.04–0.06 (0.04), SL 0.77–0.85 (0.83), EL 0.16–0.20 (0.18), ACL 0.66–0.71 (0.69), ML 1.19–1.32 (1.26), PrW 0.52–0.58 (0.55), PSL 0.10–0.13 (0.12), SDL 0.11–0.13 (0.11), PL 0.43–0.47 (0.45), PH 0.25–0.28 (0.27), PW 0.19–0.21 (0.20), PPL 0.27–0.31 (0.30), PPH 0.25–0.27 (0.26), PPW 0.25–0.28 (0.26), MFL 1.00–1.13 (1.08), MTL 0.77–0.87 (0.82), CI 87–92 (92), SI 94–101 (96), REL 21–24 (21), FLI 24–26 (25), PSI 0.9–1.0 (1.0), MFI 71–84 (80), ACI1 62–66 (63), ACI2 82–91 (83).
Medium- to large-sized species; general body color mostly black, with patches of dark brown; appendages black to orange-brown, lighter at extremities; setae dark brown; mandible with 6 teeth, but two teeth nearest basal tooth usually worn and indistinct; basal margin of mandible straight, without basal notch or deep depres- sion; mandible mostly smooth and shining, with scattered piligerous punctae; anterior clypeal margin with a median emargination; median lobe of clypeus smooth and shiny, lacking carinae, remainder of clypeus smooth and shiny; posterior ex- tension of clypeus between antennal insertions of moderate to wide width (PCW 0.04–0.06), sides slightly hourglass-shaped; frontal lobes of moderate width (FLD 0.19–022, FLI 24–26), not obscuring torular lobes in full-face view; head roughly oval-shaped, distinctly longer than broad (CI 87–92), with posterior margin slightly depressed medially; eye relatively large (EL 0.16–0.20, REL 21–24), roughly oval- shaped, with 9–10 ommatidia at greatest diameter; head almost completely smooth and shiny, with short faint longitudinal carinulae around midline of face near anten- nal lobes; scape relatively long (SI 94–101), just reaching posterior margin of head when laid back; scape surface smooth and shiny, except for scattered piligerous punctae; funiculus with a somewhat distinct antennal club; mesosoma almost completely smooth and shining, except for shallow furrows along metanotal grove, and scattered piligerous punctae; promesonotum in profile low-domed and asymmetrical, with the apex slightly anterior of midpoint; metanotal grove shallow, but distinct; propodeal spines reduced to small tubercles (PSL 0.10–0.13, PSI 0.9–1.0); petiole of moderate length (PL 0.43–0.47, PL/HW 0.52–0.57); petiolar node in profile nearly symmetrical, and of moderate height (PH/PL 0.57–0.60), dorsum smoothly rounded; postpetiole bulging and distinctly wider than petiole (PW/PPW 0.72–0.78), anterior face long and shield-like, posterior face short and truncate; petiole and postpetiole al- most completely smooth and shining, with some faint punctae confined mostly to the ventral surfaces; gaster with an elongate anterior constriction and with faint dorsal striae, remainder of gaster smooth and shiny, except for piligerous punctae; most of body dorsum with a layer of moderately long and stout standing pilosity; scape with suberect to decumbent setae; gaster with a layer of suberect setae, and a very sparse layer of short decumbent setae; legs with mostly appressed setae, but some suberect setae on coxae and femoral venters.
Queen description. (1 measured) HL 0.99, HW 0.89, FLD 0.24, PCW 0.06, SL 0.85, EL 0.26, ACL 0.72, ML 1.53, PrW 0.83, PSL 0.16, SDL 0.15, PL 0.58, PH 0.34, PW 0.25, PPL 0.35, PPH 0.32, PPW 0.33, MFL 1.16, MTL 0.89, CI 90, SI 95, REL 29, FLI 27, PSI 1.1, MFI 77, ACI1 62, ACI2 85.
Same as worker except for standard queen modifications and as follows: face with a few distinct carinulae extending from frontal lobes to ocelli; mesoscutum, near posterior margin, and scutellum, with some longitudinal carinulae/rugulae.
This taxon was previously known by the morphospecies code mgb68.
Stenamma atribellum is a distinctive species that should not be confused with any other Middle American clade Stenamma species. Molecular phylogenetic data show that it is sister to S. callipygium, which is the only other Stenamma species to have an elongate anterior gastral constriction (Branstetter unpublished data). This character joins S. atribellum and S. callipygium in the atribellum species group. Stenamma atribellum can be separated from S. callipygium by its completely smooth and shiny sculpture and emarginate anterior clypeal margin. Furthermore, these species have not been collected in sympatry and both appear to be narrow endemics.
Stenamma atribellum might be confused with the superficially similar S. alas and S. expolitum, which are both mostly smooth and shiny. However, these latter species do not have the anterior constriction of the gaster elongate and they tend to have more facial sculpture (especially in S. alas). These species are also geographically separated from one another.
The specific epithet atribellum is derived from the greek words atri- and bellu- which roughly translate into black beast.
Type material. Holotype worker. HONDURAS: Cortés, Parque Nacional Cusuco, 15.50739°N, 88.23373°W ±20m, 2030m, 3 Jun 2010, cloud forest, nest under bark of log (M. G. Branstetter, collection MGB1606) [USNM, specimen CASENT0622351]. Paratypes: same data as holotype [1w, CAS, CASENT0623237], [1w, EAPZ, CASENT0623238], [1w, ECOSCE, CASENT0623239], [1w, FMNH, CASENT0623240], [1w, ICN, CASENT0623241], [1w, INBio, CASENT0623242], [1w, JTLC, CASENT0623525], [1w, LACM, CASENT0623243], [1w, MGBPC, CASENT0623525], [1w, MCZ, CASENT0623244], [1w, MZSP, CASENT0623245], [1w, UCD, CASENT0623246], [1w, UNAM, CASENT0623247], [1dq, 1w, USNM, CASENT0622349], [1w, UVGC, CASENT0623077].
Branstetter, M. G. 2012. Origin and diversification of the cryptic ant genus Stenamma Westwood (Hymenoptera: Formicidae), inferred from multilocus molecular data, biogeography and natural history. Systematic Entomology 37:478-496. 10.1111/j.1365-3113.2012.00624.x.
Branstetter, M. G. 2013. Revision of the Middle American clade of the ant genus Stenamma Westwood (Hymenoptera, Formicidae, Myrmicinae). ZooKeys 295:1-277. doi: 10.3897/zookeys.295.4905.
Found most commonly in these habitats: 2 times found in cloud forest.
Found most commonly in these microhabitats: 1 times nests under bark of log, 1 times ex sifted leaf litter.
Collected most commonly using these methods: 1 times search, 1 times Berlese.
Elevations: collected from 1550 - 2030 meters, 2006 meters average
Collect Date Range: collected between 1994-08-26 and 2010-06-03
Type specimens: Paratype Stenamma atribellum: casent0622349