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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.
Branstetter (2013): Mexico (Atlantic slope) to Ecuador. No records from El Salvador.
J. Longino (Ants of Costa Rica): Mexico, Honduras (type locality), Costa Rica, Colombia. Costa Rica: commmon in wet montane forest throughout country, decreasing in abundance at low elevation; low density element at La Selva Biological Station.
Stenamma felixi is one of the most widespread and common species of MAC Stenamma. It occurs from approximately 50–1600 m, but is most common above 500 m, and is always found in wet forest environments, ranging from lowland rainforest to cloud forest. Workers have been collected by sifting leaf litter, beating and sweeping vegetation, baiting, using pitfall and Malaise traps, and by general searching. Nests are generally quite large and have been found in rotting logs on the ground, in tree stumps, under bark of logs, and rarely in mud banks. A few lone foundresses have been found under rotting epiphyte clumps in old treefalls, and some workers have been collected from orchids at quarantine in the U.S. All colonies collected so far have been monogynous. Workers seem to be epigeic, solitary foragers, but nothing is known about dietary preference. A very common experience is to find lone, stray workers running across medium- to large-sized logs in forest.
J. Longino (Ants of Costa Rica):
Stenamma felixi occurs in wet forest habitats from 50m elevation rainforest to 1600m elevation cloud forest. It is rare at low elevation and relatively common above 500m. Workers can be encountered in Winkler samples of sifted leaf litter, Malaise trap samples, and sweep net samples. They appear to be epigaeic foragers, and perhaps they forage on low vegetation, but I never encounter them more than a meter above the ground. The workers are relatively large and conspicuous, and I often collect diurnal foragers. I do not know what they eat; foragers are solitary and they generally do not come to baits.
I have found relatively populous nests in dead wood on the ground, in rotten stumps or under loose bark of soft rotten logs. Colonies appear to be monogynous. Although I usually find nests in dead wood, I have found scattered lone foundresses under rotting epiphyte mats in old treefalls.
In my collection records I have more nest collections of Stenamma felixi than collections from Winkler samples. This is in striking contrast to most other species of Stenamma, where nests are rarely collected or unknown and the species is mainly known from Winkler samples.
Worker diagnosis. Integument mostly black to dark brown; medium- to large-sized species (see HL, ML, PrW below); anterior clypeal margin with a median emargination; basal margin of mandible straight to slightly sinuous, without a basal notch or depression; head and mesosoma usually densely sculptured, with sharp carinae, rugae, or rugoreticulae; eye relatively large (EL 0.16–0.20, REL 18–22), oval-shaped, with 8–11 ommatidia at greatest diameter; propodeal spines absent, propodeum forming shallow, blunt angles where propodeal dorsum and declivity converge (PSL 0.07–0.11, PSI 0.8–1.1); setae on gastral tergites mostly sparse, long, and suberect, only sometimes with a few short decumbent setae; frontal lobes of moderate width (FLD 0.22–0.26, FLI 25–29), not completely obscuring torular lobes in full face view; metafemur relatively long (MFI 75–88).
Worker description. (10 measured) HL 0.90–1.19 (1.00), HW 0.81–1.04 (0.87), FLD 0.22–0.26 (0.22), PCW 0.04–0.09 (0.05), SL 0.69–0.95 (0.81), EL 0.16–0.20 (0.17), ACL 0.70–0.92 (0.79), ML 1.25–1.62 (1.37), PrW 0.58–0.74 (0.62), PSL 0.07–0.11 (0.09), SDL 0.07–0.13 (0.08), PL 0.41–0.52 (0.45), PH 0.25–0.32 (0.29), PW 0.16–0.23 (0.23), PPL 0.24–0.33 (0.28), PPH 0.21–0.27 (0.23), PPW 0.18–0.27 (0.18), MFL 0.93–1.28 (1.08), MTL 0.71–0.98 (0.81), CI 83–90 (87), SI 84–101 (93), REL 18–22 (20), FLI 25–29 (26), PSI 0.8–1.1 (1.1), MFI 75–88 (81), ACI1 57–62 (59), ACI2 93–102 (97).
Medium- to large-sized species; general body color mostly black to dark brown, with appendages lighter, brown to orange-brown toward extremities; setae dark gold-brown; mandible with 5–6 teeth, consisting of 4 distinct apical teeth, a basal tooth, and 1 tooth in between, which is smaller and often effaced; basal margin of mandible straight to slightly sinuous, without a basal notch or depression; mandible mostly smooth, except for scattered piligerous punctae, and some lateral striations; anterior clypeal margin with a shallow median emargination; median lobe of clypeus with at least a pair of distinct longitudinal carinulae that diverge toward anterior margin, sometimes with a few additional faint carinulae, apex of lobe smooth, or with some faint transverse carinulae; remainder of clypeus mostly smooth and shiny; posterior extension of clypeus between frontal lobes of moderate width (PCW 0.04–0.09), sides subparallel to slightly hour-glass-shaped; frontal lobes of moderate width (FLD 0.22–0.26, FLI 25–29), not greatly obscuring torular lobes in full face view; head usually roughly oval-shaped, but some populations with posterior margin distinctly broader than anterior margin, making head appear more triangular (CI 83–90), posterior margin always depressed medially; eye relatively large (EL 0.16–0.20, REL 18–22), oval-shaped, with 8–11 ommatidia at greatest diameter; face densely sculptured, but sculpture type variable, most often with some longitudinal rugae/carinae along midline, transitioning to rugoreticulae toward lateral margins, but sometimes face almost completely rugoreticulate, or completely carinate, depth and sharpness of sculpture variable; scape of moderate length (SI 84–101), just reaching posterior margin of head when laid back; scape surface mostly smooth, but with distinct carinulae, and scattered piligerous punctures; scape sometimes appearing thickened and more robust; flagellum with distinct 4-segmented antennal club; mesosoma mostly densely sculptured, but sculpture type variable; dorsum of pronotum usually rugose (longitudinal orientation) to rugoreticulate, but sometimes carinate, anterior declivity of pronotum with transverse carinulae; dorsum of mesonotum rugoreticulate to transversely carinate, sometimes intermediate; side of pronotum rugulose to carinate; katepisternum mostly smooth, with some rugulae on upper half; dorsum and declivity of propodeum transversely carinate/carinulate; side of propodeum rugose; promesonotum in profile domed (higher than average), symmetrical to slightly asymmetrical, with location of apex variable; metanotal groove distinct, but narrow; dorsum of propodeum in profile distinctly longer than declivity; propodeal spines absent, propodeum forming shallow, blunt angles where dorsum and declivity converge (PSL 0.07–0.11, PSI 0.8–1.1); petiole of moderate length (PL/HW 0.48–0.55); petiolar node of moderate height (PH/PL 0.60–0.64), subconical in shape, usually pointing vertically to only slightly posteriad, dorsum narrowly to somewhat broadly rounded, posterior margin of petiole, where postpetiole inserts, distinctly bent downwards; postpetiole in profile nearly symmetrical, with anterior face slightly longer than posterior face, postpetiole similar in size to petiolar node (PPH/PH 0.78–0.85); petiole and postpetiole usually mostly punctate, with only anterior faces of nodes smooth, but sometimes nodes mostly smooth, with punctae faint; gaster smooth, with scattered piligerous punctae; most of body dorsum with standing pilosity; setae on gastral tergites mostly sparse, long, and suberect, only sometimes with a few short decumbent setae; setae on scapes subdecumbent to appressed; setae on legs decumbent to appressed, with a few suberect setae on femoral venters and coxae.
Queen description. (6 measured) HL 1.00–1.17 (1.07), HW 0.85–0.98 (0.89), FLD 0.25–0.27 (0.25), PCW 0.05–0.08 (0.07), SL 0.76–0.92 (0.84), EL 0.23–0.30 (0.29), ACL 0.69–0.91 (0.83), ML 1.45–1.75 (1.57), PrW 0.79–0.91 (0.83), PSL 0.11–0.15 (0.13), SDL 0.12–0.16 (0.14), PL 0.51–0.59 (0.55), PH 0.31–0.36 (0.33), PW 0.21–0.25 (0.23), PPL 0.30–0.37 (0.35), PPH 0.26–0.31 (0.29), PPW 0.26– 0.32 (0.31), MFL 0.96–1.27 (1.11), MTL 0.74–0.95 (0.85), CI 83–88 (83), SI 87–97 (94), REL 27–32 (32), FLI 27–30 (28), PSI 0.9–1.0 (0.9), MFI 76–88 (81), ACI1 58–61 (59), ACI2 90–99 (99).
Same as worker except for standard queen modifications and as follows: pronotum transversely carinulate; mesoscutum longitudinally carinulate, or carinate; scutellum rugoreticulate, or longitudinally carinulate to carinate; propodeum with transverse carinulae/carinae that wrap around surface; mesopleuron usually mostly smooth; pi- losity on gastral tergites clearly bilayered, with a sparse layer of long, suberect setae, and a dense layer of appressed pubescence; wing venation in specimen CASENT0622308.
Male. See specimen CASENT0622311.
This species is rather distinctive with its large size, lack of propodeal spines, and dense sculpturing. It should not be easily confused with any other Middle American clade species.
Over its range, S. felixi shows considerable variation in the density and orientation of its sculpturing as well as in petiole shape. However, Branstetter (2013) only identifies one distinct variant (CASENT0622555) which is described in more detail. Specimens from Nicaragua and Costa Rica have very deep carinate sculpturing on the face and mesosoma. The facial carinae are usually longitudinal, but occasionally reticulate laterad. The pronotal dorsum has longitudinal carinae, but the side of the pronotum has arcuate carinae that wrap across the dorsum of the metanotum. The head in profile view has a very distinctive shape, in which the posterior margin of the head is very wide compared to the anterior margin, giving the head a somewhat triangular appearance. Lastly, the petiolar and postpetiolar nodes are noticeably smooth. Specimens from Colombia and Ecuador and from north of Nicaragua lose the carinate sculpture. All of the slight sculpture differences among popluations are treated as intraspecific variation as there is no evidence of sympatry among forms.
Stenamma felixi Mann, 1922: 21, fig. 10. Lectotype worker: HONDURAS, [Atlántida]: San Juan Pueblo, [ca. 15.583°N, 87.233°W], Feb–Mar 1920 (W. M. Mann) (USNM, Cotype. No. 24448, pin CASENT0126355, bottom specimen) (USNM) [examined]. Smith, 1962: 34, worker description. Branstetter, 2009: phylogeny. Branstetter, 2012: phylogeny. Branstetter, 2013: worker, queen descriptions and images; male images.
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: 89 times found in montane wet forest, 50 times found in cloud forest, 11 times found in mesophyll forest, 5 times found in montane tropical rainforest, 13 times found in mature wet forest, 2 times found in mixed hardwood forest bordering stream, 8 times found in montane rainforest, 8 times found in wet forest, 4 times found in lowland rainforest, 6 times found in cloud forest, primary, near ridgetop, ...
Found most commonly in these microhabitats: 1 times carrion-baited pitfall traps, 119 times ex sifted leaf litter, 34 times at bait, 3 times nest in log, 12 times hojarasca, 9 times beating vegetation, 1 times ex orchids, 6 times sifted litter (leaf mold, rotten wood), 5 times ex rotten log, 1 times nest in rotten wood, 3 times ex log, ...
Collected most commonly using these methods: 1 times pitfall, 50 times search, 91 times MiniWinkler, 32 times baiting, 23 times Winkler, 19 times Berlese, 12 times MaxiWinkler, 18 times Mini Winkler, 9 times Beating, 2 times quarantine, 8 times flight intercept trap, ...
Elevations: collected from 30 - 3050 meters, 1130 meters average
Type specimens: Lectotype (bottom specimen) Stenamma felixi: casent0126355