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Species: Stenamma zelum   Branstetter, 2013 

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Taxonomic History (provided by Barry Bolton, 2020)

Stenamma zelum Branstetter, 2013 PDF: 269, figs. 168-171 (w.q.) NICARAGUA. Neotropic. AntCat AntWiki


This species belongs to the Middle American clade of Stenamma (see Branstetter 2012). All conent on this page modified from Branstetter (2013) unless noted otherwise.

// Distribution


  Geographic regions (According to curated Geolocale/Taxon lists):
    Americas: Costa Rica, Honduras, Nicaragua, Panama
  Biogeographic regions (According to curated Bioregion/Taxon lists):

Distribution Notes:

Honduras to Panama.


Stenamma zelum is known almost exclusively from Winkler and Berlese samples of sifted leaf litter. Only once has a stray individual (a dealate queen) been collected by general searching. This species is found from 350–1700 m elevation, but is most common at mid-elevations around 1000 m. It inhabits mature wet forest environments, such as montane rainforest and cloud forest.


Worker diagnosis. Integument mostly dark red-brown to brown; medium to large-sized species (see HL, ML, PrW below); head and promesonotum mostly foveate to coarsely rugoreticulate; eye relatively small (EL 0.10–0.13, REL 12–16), somewhat bulging, subcircular to slightly oval-shaped, with 6–8 ommatidia at greatest diameter; gastral pilosity long, dense, and mostly suberect; propodeal spines reduced to sharp angles or small tubercles (PSL 0.12–0.16, PSI 1.0–1.3); anterior clypeal margin with a median excavation containing 2 sharp outer teeth and 2 smaller inner teeth (sharp to blunt); basal margin of mandible straight to slightly sinuous, without a basal notch or depression. 

Similar species: Stenamma brujita.

     Worker description. (11 measured) HL 0.87–1.03 (0.99), HW 0.78–0.92 (0.85), FLD 0.26–0.31 (0.29), PCW 0.04–0.08 (0.07), SL 0.67–0.80 (0.74), EL 0.10–0.13 (0.11), ACL 0.58–0.69 (0.60), ML 1.15–1.38 (1.29), PrW 0.55–0.67 (0.63), PSL 0.12–0.16 (0.14), SDL 0.10–0.16 (0.13), PL 0.46–0.56 (0.53), PH 0.25–0.29 (0.29), PW 0.17–0.21 (0.20), PPL 0.27–0.32 (0.32), PPH 0.22–0.27 (0.25), PPW 0.21– 0.26 (0.24), MFL 0.82–0.99 (0.93), MTL 0.65–0.80 (0.73), CI 86–92 (86), SI 83–89 (86), REL 12–16 (13), FLI 31–34 (34), PSI 1.0–1.3 (1.1), MFI 91–98 (92), ACI1 65–68 (65), ACI2 82–89 (82).
     Medium to large-sized species; general body color mostly dark red-brown, with patches of brown and orange-brown on gaster, appendages lighter; setae golden brown; mandible with 6–9 teeth, consisting of 3 distinct apical teeth, a distinct basal tooth, and 2–5 inner teeth/denticles, which are usually worn and indistinct; basal margin of mandible straight to slightly sinuous, without a basal notch or depression; mandible mostly smooth and shiny, with scattered piligerous punctae and faint striae; anterior clypeal margin viewed from an anterodorsal angle with a median excavation containing 2 sharp outer teeth and 2 smaller inner teeth, which are sharp to blunt, and recessed behind median lobe of clypeus (not visible with mandibles closed); median lobe of clypeus usually with a pair of faint carinulae that diverge toward the anterior margin, apex of lobe with a short transverse carinula, remainder of clypeus mostly smooth and shiny, sometimes with a few additional rugulae on median lobe; posterior extension of clypeus between antennal insertions of moderate width (PCW 0.04–0.08), sides subparallel to slightly diverging posteriad; frontal lobes well-developed, but not completely covering torular lobes in full-face view (FLD 0.26–0.31, FLI 31–34); head appearing subrectangular (CI 86–92), with posterior margin depressed medially; eye relatively small (EL 0.10–0.13, REL 12–16), somewhat bulging, subcircular to slightly oval-shaped, with 6–8 ommatidia at greatest diameter; face usually strongly foveate to coarsely rugoreticulate, with a few longitudinal costae along midline, interstices with piligerous punctae, some high-elevation populations with face sculpture more polished and effaced, especially on side of head, which can be smooth and shiny; scape relatively short (SI 83–89), not reaching posterior margin of head when laid back; scape surface mostly smooth and shiny, with scattered piligerous punctae; flagellum with an indistinct 4-segmented antennal club; mesosoma usually densely sculptured, with promesonotum mostly foveate (especially on dorsum) and remaining surfaces foveate to rugoreticulate or rugose, in some high-elevation populations sculpture is reduced, with foveae on promesonotal dorsum appearing more like transverse furrows, and with side of promesonotum largely smooth and shiny; propodeal declivity mostly smooth and shiny, usually with a few transverse carinulae; promesonotum in profile low-domed, slightly asymmetrical, with the apex shifted anteriorly; anterior face of promesonotum longer and steeper than posterior face and mostly smooth; metanotal groove well-demarcated, of moderate width and depth; propodeal spines forming sharp angles or at most small tubercles (PSL 0.12–0.16, PSI 1.0–1.3); petiole relatively long (PL/HW 0.58–0.63), with node of average size (PH/PL 0.51–0.54); node in profile variable, usually forming a small roughly symmetrical dome with a rounded dorsum, but sometimes dome more asymmetrical with anterior face longer than posterior face, and sometimes with apex more sharp and positioned anterior of midpoint; postpetiole somewhat elongate (PPH/PPL 0.79–0.88) and globular, about the same height and volume as petiolar node (PPH/PH 0.88–0.98), postpetiolar node asymmetrical, with anterior face longer than posterior face; venter of postpetiole in profile usually distinctly sinuous, with anteroventral margin forming a small process; petiolar and postpetiolar nodes mostly smooth and shiny, remaining waist surfaces faintly punctate; gaster mostly smooth and shiny, with scattered piligerous punctae; most of body with a moderately dense layer of long suberect to subdecumbent pilosity; scape with layer of longer sparser suberect setae and layer of shorter subdecumbent setae; gastral setae not distinctly bilayered, forming a moderately dense layer of long suberect to subdecumbent setae; setae on legs suberect to decumbent, with longer suberect hairs on coxae and femoral venters.
     Queen description. (5 measured) HL 0.86–1.01 (0.92), HW 0.78–0.90 (0.84), FLD 0.27–0.32 (0.29), PCW 0.05–0.09 (0.06), SL 0.67–0.78 (0.71), EL 0.16–0.20 (0.17), ACL 0.59–0.67 (0.61), ML 1.25–1.48 (1.33), PrW 0.68–0.79 (0.71), PSL 0.15–0.19 (0.17), SDL 0.13–0.18 (0.14), PL 0.52–0.58 (0.54), PH 0.26–0.31 (0.28), PW 0.19–0.23 (0.21), PPL 0.31–0.33 (0.33), PPH P0.24–0.28 (0.25), PW 0.19– 0.23 (0.21), MFL 0.83–0.98 (0.89), MTL 0.67–0.78 (0.69), CI 88–93 (92), SI 83–88 (84), REL 20–23 (20), FLI 33–35 (34), PSI 1.1–1.2 (1.1), MFI 92–94 (94), ACI1 65–67 (65), ACI2 83–89 (86).
     Same as worker except for standard queen modifications and the following: mesoscutum foveate, except for a longitudinal strip of completely smooth cuticle, which crosses the entire surface; mesopleuron mostly smooth and shiny; propodeum carinate to rugose, with sculpture transversely wrapping around surface; wing venation as in specimen CASENT0621980.
     Male. Unknown.


Stenamma zelum is a very distinctive species, unlikely to be confused with anything else. The only exception being S. brujita, which is not closely related, but has many convergent traits (e.g. size and sculpture). Separation of these two species is discussed in detail in the comments section under S. brujita, but I will restate here that these species have not been collected in sympatry, and should be easy to separate using locality data alone.

Molecular phylogenetic results indicate that S. zelum is sister to the expolitum species group, which includes S. alas, S. expolitico, and S. expolitum (Branstetter 2012). However, S. zelum is distinct from these species and shares none of the diagnostic morphological character states of the species group.

Within S. zelum, Branstetter (2013) describes two morphotypes, the more common form, represented by the type series (CASENT0622535), and a high elevation form (variant 1; INBIOCRI001280618), which is known only from a few sites above 1500 m in Costa Rica (e.g. 9km NE Vara Blanca, Est. Pittier, Las Alturas Biological Station). The variant has reduced sculpturing, in which the foveae have become less distinct, and large smooth patches are present on the side of the head and pronotum. Also, the clypeal teeth are reduced, with the inner teeth blunt and nearly absent.

Preliminary molecular phylogenetic results, which include several populations of each morphotype, show that the two forms separate into sister clades, suggesting that the high-elevation variant may represent a distinct species. However, Branstetter (2013) chooses to recognize one species and states that variation within the high-elevation form needs to be better understood.

Taxonomic Notes:

Type material. Holotype worker. NICARAGUA, Jinotega: Parque Nacional Cerro Saslaya, 13.77148°N, 85.01152°W ±10m, 1110m, 12 May 2011, ridgetop cloud forest, ex sifted leaf litter (LLAMA, collection Wa-D-03-1-35) [USNM, specimen CASENT0622535]. Paratypes: same data as holotype [1w, CAS, CASENT0622534], [1w, EAPZ, CASENT0622536]; same data but 13.77077°N, 85.00156°W ±20m, 850m, 8 May 2011 (LLAMA, Wm-D-02-2-02) [1w, ECOSCE, CASENT0623510], [1w, FMNH, CASENT0623511], [1w, ICN, CASENT0623512], [1dq, 1w, INBio, CASENT0623508, CASENT0623513], [1w, JTLC, CASENT0623514], [1w, LACM, CASENT0623515], [1dq, 1w, MGBPC, CASENT0623509, CASENT0623516]; 13.77000°N, 85.00326°W ±20m, 920m, 8 May 2011 (LLAMA, Wm-D-02-2-03) [1dq, 1w, MCZ, CASENT0623517, CASENT0623519], [1w, MZSP, CASENT0623520], [1w, UCD, CASENT0623521], [1w, UNAM, CASENT0623522], [1dq, 1w, USNM, CASENT0623518, CASENT0623523], [1w, UVGC, CASENT0623524].


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.

Specimen Habitat Summary

Found most commonly in these habitats: 99 times found in montane wet forest, 18 times found in ridgetop cloud forest, 26 times found in ridgetop cloud forest, isolated peak with oak trees, 10 times found in mature wet forest, 11 times found in cloud forest, primary, near ridgetop, 7 times found in wet forest, 3 times found in tropical rainforest, 5 times found in cloud forest, probably old second growth, matrix of dense bamboo and more open forest, 6 times found in cloud forest edge, near dairy farm pasture, some big trees in rocky areas, probably disturbed primary or old second growth, on a steep slope, 3 times found in tropical rainforest, with big trees, probably primary, ...

Found most commonly in these microhabitats: 109 times ex sifted leaf litter, 78 times Hojarasca, 1 times wet forest litter, 2 times sifted litter, 2 times suelo, 1 times suelo suspendido, 1 times strays, 1 times raices helecho, 1 times night foragers, 1 times Mixed primary forest litter & soil, 1 times material suspendido, ...

Collected most commonly using these methods: 84 times miniWinkler, 79 times Mini Winkler, 12 times maxiWinkler, 15 times Winkler, 10 times Berlese, 2 times search, 1 times baiting.

Elevations: collected from 250 - 1670 meters, 1010 meters average

Collect Date Range: collected between 1973-01-18 and 2020-01-10

Type specimens: Holotype Stenamma zelum: casent0622535; Paratype Stenamma zelum: casent0622534, casent0622536

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