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Taxonomic History (provided by Barry Bolton, 2017)

Overview:

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:

(based on species list records)
Neotropical Region: Americas, Central America, Mexico, Oaxaca

Distribution Notes:

Southern Mexico (Oaxaca). Known only from the type locality.

Biology:

Stenamma andersoni is recorded from a single Berlese sample of sifted leaf litter collected in cloud forest at 990 m elevation.

Identification:

Worker diagnosis. Integument brown to red-brown (note that observed speci- mens are old, fresh specimens probably darker); small-sized species (see HL, ML, PrW below); anterior clypeal margin undulating, forming 2–4 small blunt teeth; basal margin of mandible sinuous, with a shallow basal depression, but without a basal tooth; head and pronotum mostly smooth and shiny; promesonotum in profile with relatively sharp transitions between anterior and dorsal faces, and between pronotum and mesonotum; pilosity on gastral tergites forming a layer of stout suberect setae, and a sparse layer of decumbent setae; eye of moderate size (EL 0.08–0.09, PSL 0.08–0.10), oval-shaped, with 5 ommatidia at greatest diameter; propodeal spines tuberculate (PSL 0.08–0.10, PSI 1.2–1.3); frontal lobes of moderate width (FLD 0.12–0.13, FLI 23– 24), not obscuring torular lobes in full-face view.

Similar species: Stenamma connectum, S. crypticum, S. huachucanum, S. maximon.

     Worker description. (2 measured) HL 0.60–0.63 (0.63), HW 0.50–0.55 (0.55), FLD 0.12–0.13 (0.13), PCW 0.03 (0.03), SL 0.49–0.52 (0.52), EL 0.08–0.09 (0.09), ACL 0.47–0.49 (0.49), ML 0.76–0.81 (0.81), PrW 0.36–0.39 (0.39), PSL 0.08–0.10 (0.10), SDL 0.06–0.08 (0.08), PL 0.27–0.29 (0.29), PH 0.16–0.19 (0.19), PW 0.12– 0.13 (0.13), PPL 0.15–0.16 (0.16), PPH 0.14–0.16 (0.16), PPW 0.16–0.17 (0.17), MFL 0.54–0.57 (0.57), MTL 0.42–0.45 (0.45), CI 85–88 (85), SI 95–98 (95), REL 16–17 (17), FLI 23–24 (23), PSI 1.2–1.3 (1.2), PI 53–54 (53), MFI 93–97 (97), ACI1 68 (68), ACI2 94–96 (94).      
     Small-sized species; general body color brown to red-brown (note observed specimens are older, fresh material almost certainly darker), with appendages lighter, brown to yellow-brown at extremities; setae golden; mandible with 6 teeth; basal margin of mandible sinuous, with a shallow basal depression, but no basal tooth; mandible mostly smooth, except for some conspicuous basal striae, and scattered piligerous punctae; anterior clypeal margin undulating, forming 2–4 small blunt teeth; median lobe of clypeus smooth, without noticeable carinulae, apex of lobe with a short transverse carinulae, remainder of clypeus smooth and shiny; posterior extension of clypeus between antennal insertions somewhat narrow (PCW 0.03), with sides subparallel; frontal lobes of moderate width (FLD 0.12–0.13, FLI 23–24), not obscuring torular lobes in full- face view; head roughly oval-shaped (CI 85–88), posterior margin with a slight median depression; eye of moderate size (EL 0.08–0.09, REL 16–17), oval-shaped, with 5 ommatidia at greatest diameter; face almost completely smooth and shiny, except for a few carinulae around frontal lobes and on genae, and scattered piligerous punctae; scape of moderate length (SI 95–98), not quite reaching posterior margin when laid back; scape surface mostly smooth, with faint striations, and scattered piligerous punctae; flagellum with a distinct 4–segmented antennal club; all of pronotum and most of mesonotal dorsum smooth and shiny, anepisternum rugose, katepisternum punctate, side of propodeum mostly punctate, with a few rugulae, dorsum and declivity of propodeum with transverse carinulae; promesonotum in profile low-domed, roughly symmetrical, with relatively sharp (and distinctive) transitions between anterior and dorsal faces, and between pronotum and mesonotum; metanotal groove of well-demarcated, of moderate width and depth; propodeal spines tuberculate (PSL 0.08–0.10, PSI 1.2– 1.3); petiole appearing of moderate length (PL/HW 0.53–0.54); petiolar node in profile of moderate height (PH/PL 0.60–0.65), roughly symmetrical, with anterior and posterior faces almost equal in length, node dorsum rounded, but somewhat narrow, pointing vertically; postpetiole in profile subspherical, slightly smaller than petiolar node (PPH/PH 0.84–0.86); petiole and postpetiole mostly lightly punctate, with anterior faces of nodes smooth; gaster mostly smooth and shiny, with scattered piligerous punctae; most of body dorsum with thickened standing pilosity; pilosity on gastral tergites forming a layer of stout suberect setae, and a sparse layer of decumbent setae; setae on scapes dense, decumbent to appressed; setae on legs mostly appressed, with a few suberect to subdecumbent setae on femoral venters and coxae.
     Queen. Unknown.
     Male. Unknown.

Comments:

This taxon was previously known by the morphospecies code mgb71.

Stenamma andersoni should be easy to separate from similar species by its smooth head and pronotum, unique pronotum shape, and thickened gastral setae.

Stenamma andersoni is known from only two specimens collected in 1987. As a result, the specimens examined in Branstetter (2013) are somewhat faded in color and were not useable for molecular phylogenetic work. With morphology alone, it is not clear to which species S. andersoni is most closely related, but Branstetter (2013) hypothesizes that it is probably near S. crypticum or S. huachucanum.

Stenamma andersoni is named after the distinguished weevilologist Robert S. Anderson, who's indefatiguable collecting efforts and intense focus on leaf litter arthropods are responsible for uncovering this species.

Taxonomic Notes:

Type material. Holotype worker. MÉXICO, Oaxaca: 10.9km N. Candelaria, [ca. 16.220°N, 95.891°W], 990m, 12 Jul 1987, cloud forest, ex sifted leaf litter (R. S. Anderson, collection RSA87-15) [USNM, specimen CASENT0604603]. Paratype: same data as holotype [1w, UNAM, CASENT0604602].

References:

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: 1 times found in cloud forest.

Found most commonly in these microhabitats: 1 times ex sifted leaf litter.

Collected most commonly using these methods: 1 times Berlese.

Elevations: collected at 991 m

Type specimens:

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