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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.
Southern Mexico to Honduras. No records from El Salvador.
Stenamma saenzae is known almost exclusively from extracts of sifted leaf litter, with only a few queens collected from flight intercept traps in Belize. It is restricted to montane wet forest environments (e.g. cloud forest, mesophyll forest, pine cloud forest, oak-pine forest, liquidambar-oak-pine forest) and has been collected from 1000–2100 m elevation. Dealate queens as well as workers are commonly collected from leaf litter, suggesting that nests might be located within this stratum.
Worker diagnosis. Integument mostly brown to orange-brown and mottled; small-sized species (see HL, ML, PrW below); basal margin of mandible sinuous, always with a basal notch containing a small tooth; anterior clypeal margin undulating, often forming 4 blunt teeth; face completely sculptured, usually mostly rugoreticulate; gastral pilosity with a dense layer of short decumbent to appressed setae, and a sparse layer of longer suberect setae; eye small (EL 0.05–0.09, REL 10–16), subcircular, with 3–5 ommatidia at greatest diameter; posterior extension of clypeus between antennal insertions narrow (PCW 0.01–0.02), with inner margins of frontal lobes almost touching anteriorly; scape short (SI 81–92), not reaching posterior margin of head when laid back; propodeal spines tuberculate to short (PSL 0.07–0.14, PSI 1.5–2.3).
Similar species: Stenamma crypticum, S. excisum, S. nanozoi.
Worker description. (16 measured) HL 0.52–0.69 (0.65), HW 0.43–0.59 (0.54), FLD 0.11–0.14 (0.14), PCW 0.01–0.02 (0.02), SL 0.36–0.50 (0.50), EL 0.05–0.09 (0.07), ACL 0.37–0.49 (0.47), ML 0.60–0.82 (0.77), PrW 0.30–0.41 (0.38), PSL 0.07–0.14 (0.10), SDL 0.04–0.07 (0.06), PL 0.23–0.31 (0.29), PH 0.14–0.18 (0.17), PW 0.11–0.14 (0.14), PPL 0.12–0.19 (0.16), PPH 0.12–0.17 (0.17), PPW 0.14– 0.19 (0.17), MFL 0.39–0.53 (0.51), MTL 0.32–0.44 (0.41), CI 84–89 (84), SI 81–92 (92), REL 10–16 (13), FLI 22–27 (26), PSI 1.5–2.3 (1.6), MFI 107–119 (107), ACI1 69–73 (70), ACI2 94–105 (94).
Small-sized species; general body color a mottled dark brown to light orange-brown, with mandibles and appendages lighter, usually orange-brown to yellow-brown; setae golden brown; mandible with 6–7 teeth (usually 6), consisting of 2–3 distinct apical teeth, a distinct, usually well-defined basal tooth, and 2–3 inner teeth, which are sometimes worn and indistinct; basal margin of mandible sinuous and always with a small basal notch containing a tooth; mandible mostly smooth and shining, with scattered piligerous punctae and basal striae; anterior clypeal margin viewed at an anterodorsal angle weakly to strongly undulating (appearing nearly flat in full-face view), often forming 4 blunt teeth, median undulation (emargination) sometimes narrow and notch-like; median lobe of clypeus lacking a distinct pair of longitudinal carinulae, either completely smooth, or with faint irregular striations (type population), apex of lobe with a transverse carina, remainder of clypeus mostly smooth and shiny; posterior extension of clypeus between antennal insertions very narrow (PCW 0.01–0.02), with sides subparallel and inner margins of frontal lobes almost touching anteriorly; frontal long, with 3–5 ommatidia at greatest diameter; face densely sculptured, usually mostly rugoreticulate, with longitudinal rugae medially, but sometimes reticulae less distinct and interconnected, interstices lightly punctate; scape relatively short, not reashing posterior margin of head when laid back (SI 81–92), usually of average thickness (type population), but some populations with scape distinctly swollen distally; scape cuticle mostly smooth and somewhat shiny, with scattered piligerous punctae; flagellum with somewhat distinct 4-segmented antennal club, apical segment noticeably enlarged; sculpture on mesosoma variable among populations, lateral surface usually weakly to strongly punctate, with variable number of longitudinal rugulae, dorsal surface of promesonotum variably rugulose-punctate, with pronotum ranging from completely smooth to strongly sculptured, most populations intermediate (type population), pronotum sometimes with a distinct longitudinal carina; propodeal declivity smooth and shiny or with a few transverse carinulae; promesonotum in profile low-domed and roughly symmetrical (type population), or less often flattened and more asymmetrical, with anterior face distinctly longer than posterior; propodeal spines tuberculate or forming short, broad triangular spines (PSL 0.07–0.14, PSI 1.5–2.3); metanotal grove usually well demarcated, of moderate depth and width; petiole of moderate length (PL/HW 0.47–0.56), average-looking; node in profile somewhat small (PH/PL 0.57– 0.64), subconical, with anterior face slightly longer and more sloping than posterior face, node dorsum in profile rounded, pointing vertical to slightly posteriad; postpetiole in profile subcircular, usually appearing similar in size to petiolar node (type population), but sometimes slightly larger and more bulging (PPH/PH 0.86–1.08); petiole and postpetiole lightly to somewhat strongly punctate, with nodes variably smooth and shiny; gaster mostly smooth and shiny, with scattered piligerous punctae; most of body dorsum with very short suberect to decumbent pilosity; scapes with a dense layer of decumbent to appressed setae; gastral pilosity consisting of a dense decumbent (type population) to appressed layer of setae, and a much sparser layer of suberect setae, which is sometimes difficult to see among decumbent setae; setae on legs mostly appressed, with a few suberect setae on coxae and femoral venters.
Queen description. (5 measured) HL 0.56–0.67 (0.66), HW 0.50–0.59 (0.59), FLD 0.12–0.15 (0.15), PCW 0.02–0.03 (0.03), SL 0.41–0.51 (0.51), EL 0.13–0.15 (0.15), ACL 0.41–0.51 (0.51), ML 0.77–0.92 (0.91), PrW 0.43–0.52 (0.52), PSL 0.10–0.11 (0.10), SDL 0.06–0.08 (0.07), PL 0.27–0.32 (0.32), PH 0.16–0.19 (0.19), PW 0.14–0.16 (0.16), PPL 0.15–0.19 (0.19), PPH 0.16–0.19 (0.19), PPW 0.17– 0.21 (0.21), MFL 0.44–0.55 (0.54), MTL 0.37–0.46 (0.46), CI 84–91 (89), SI 80–90 (86), REL 25–26 (26), FLI 24–27 (25), PSI 1.3–1.8 (1.5), MFI 103–115 (108), ACI1 69–72 (69), ACI2 95–100 (100).
Same as worker except for standard queen modifications and as follows: pronotum transversely rugose to rugoreticulate laterad, becoming punctate mesad; mesoscutum with narrow strip of smooth cuticle extending from anterior margin to about midpoint along midline; mesopleuron mostly smooth and shiny; propodeum mostly with transverse carinulae that wrap around surface, or less often mostly punctate; propodeal spines smaller (PSL 0.10–0.11, PSI 1.3–1.8).
Male. Unknown.
Based on overall size and form, S. saenzae might be confused with S. crypticum, S. nanozoi, or S. excisum, but out of these species, S. nanozoi is the only species to share the small tooth on the basal margin of the mandible. Stenamma saenzae can be easily separated from S. nanozoi by comparing gastral pilosity, which in the latter species, is composed mainly of a sparse layer of thickened suberect setae. Tentative molecular phylogenetic results show S. saenzae as sister to a clade that includes S. catracho, S. crypticum, and S. monstrosum (Branstetter unpublished data).
Stenamma saenzae shows considerable morphological variability among populations. From this variation, Brastetter (2013) describes two variants that differ significantly from the type phenotype (indicated above). Variant 1 (CASENT0604912) occurs mainly in central Guatemala (Biotopo Quetzal, Purulhá) and has the following distinguishing features: pronotal dorsum smooth and shiny; postpetiole more bulging, appearing larger than petiolar node; head somewhat enlarged. Although distinct from the type population, intermediate phenotypes are found at intervening localities, meaning that this variation is probably intraspecific, and likely due to environmental effects on size and sculpture. Supporting this view is the observation that the locality Biotopo Quetzal, where variant 1 is most distinct, is an especially cool, wet cloud forest site.
Variant 2 (CASENT0621764) is known from the localities La Unión in eastern Guatemala and Cusuco in northwestern Honduras, and it has the following distinguishing character states: overall body size distinctly smaller; antennal scapes thickened dis- tally; mesosoma and waist strongly punctate, with rugulae reduced; promesonotum in profile flatter, and more asymmetrical; propodeal spines larger and more broadly triangular; lower layer of gastral setae appressed (rather than decumbent), allowing the suberect layer to be clearly visible. Unlike with variant 1, intermediate phenotypes between variant 2 and other forms are not found, suggesting that this variant is more isolated and perhaps represents a distinct species. Because this variant is not sympatric with the other forms, Branstetter (2013) lumps variant 2 within S. saenzae, but notes that more data are needed to test its possible speces status. Preliminary molecular results show specimens from La Unión and Cusuco to be sister taxa, nested inside the larger S. saenzae clade.
Type material. Holotype worker. MÉXICO, Chiapas: 5km NE Coapilla, 17.17550°N, 93.13212°W, 1990m, 25 May 2008, 2° mesophyll forest, ex sifted leaf litter (LLAMA, collection Wa-A-04-1-26) [USNM, specimen CASENT0603860]. Paratypes: same data as holotype but 17.18330°N, 93.15209°W ±50m, 1915m, 25 May 2008 (LLAMA, Wa-A-04-2-07) [1dq, 1w, CAS, CASENT0623473, CASENT0623474], [1w, EAPZ, CASENT0623475], [1w, ECOSCE, CASENT0623476], [1w, FMNH, CASENT0623477], [1w, ICN, CASENT0623478]; 17.17550°N, 93.13212°W ±50m, 1990m, 25 May 2008 (LLAMA, Wa-A-04-2-06) [1w, INBio, CASENT0623469], [1w, JTLC, CASENT0623470], [1w, LACM, CASENT0623471], [1w, MGB- PC, CASENT0623472]; 17.18296°N, 93.15197°W ±50m, 1915m, 25 May 2008 (LLAMA, Wa-A-04-2-15) [1dq, 1w, MCZ, CASENT0623479, CASENT0623480], [1w, MZSP, CASENT0623481], [1w, UCD, CASENT0623482], [1w, UNAM, CASENT0623483], [1w, UVGC, CASENT0623484], [1w, USNM, CASENT0623485]; 17.18273°N, 93.15184°W ±50m, 1915m, 25 May 2008 (LLA- MA, Wa-A-04-2-21) [1dq, USNM, CASENT0603866].
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: 93 times found in cloud forest, 23 times found in 2º mesophil forest, 23 times found in mesophyll forest, 4 times found in mesic forest, 2 times found in bosque nuboso, 5 times found in cloud forest at night, 2 times found in cloud forest litter, 1 times found in pine cloud forest, 1 times found in mixed trop./temp. mesic forest, 1 times found in montane rainforest, ...
Found most commonly in these microhabitats: 163 times ex sifted leaf litter, 6 times forest litter, 1 times leaf litter, 2 times sifted litter (leaf mold, rotten wood), 1 times ex sifted log and leaf litter.
Collected most commonly using these methods: 113 times MiniWinkler, 28 times maxiWinkler, 12 times Berlese, 6 times Winkler, 9 times Berlese/Winkler, 5 times Night MiniWinkler, 1 times FIT.
Elevations: collected from 1000 - 2260 meters, 1624 meters average
Type specimens: Paratype Stenamma saenzae: casent0603866
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