Stenamma nonotch, Branstetter, Michael G., 2013

Branstetter, Michael G., 2013, Revision of the Middle American clade of the ant genus Stenamma Westwood (Hymenoptera, Formicidae, Myrmicinae), ZooKeys 295, pp. 1-277 : 164-168

Stenamma nonotch sp. n. Worker: Figures 131, 132; Queen: Figure 133; Map: Figure 130

Stenamma mgb11 [variant 2 below] Branstetter, 2012: phylogeny.

Type material.

Holotype worker. MÉXICO, Oaxaca: 4.3km SW Valle Nacional, 17.74320°N, 96.32729°W ± 40m, 370m, 13 Aug 2009, disturbed tropical rainforest, ex sifted leaf litter (L. Sáenz, collection LSD329) [USNM, specimen CASENT0605789]. Paratypes: same data as holotype [1dq, 1w, CAS, CASENT0605782, CASENT0605788], [1w, EAPZ, CASENT0605790], [1w, ECOSCE, CASENT0623408], [1w, FMNH, CASENT0623409], [1w, ICN, CASENT0623410], [1w, INBio, CASENT0623411], [1w, JTLC, CASENT0623412], [1w, LACM, CASENT0623413], [1w, MGBPC, CASENT0623414], [1dq, 1w, MCZ, CASENT0605784, CASENT0623415], [1w, MZSP, CASENT0623416], [1w, UCD, CASENT0623417], [1dq, 1w, UNAM, CASENT0605783, CASENT0623418], [1dq, 1w, USNM, CASENT0623407, CASENT0623419], [1w, UVGC, CASENT0623420].

Worker diagnosis.

Integument mostly dark red-brown (almost black) to brown; small- to medium-sized species (see HL, ML, PrW below); anterior clypeal margin entire, or at most with a nearly imperceptible median notch (only visible from anterodorsal angle); basal margin of mandible straight; face densely sculptured, mostly rugoreticulate; dorsum of promesonotum rugoreticulate, or with many irregular rugulae; pilosity on gastral tergites indistinctly bilayered, forming a somewhat sparse layer of long suberect setae, and a very sparse layer of short decumbent setae; eye of small to moderate size (EL 0.09-0.11, REL 15-19), oval-shaped, with 4-7 ommatidia at greatest diameter; propodeal spines reduced to small triangular tubercles (PSL 0.08-0.14, PSI 1.1-1.4); frontal lobes of moderate width (FLD 0.14-0.19, FLI 25-29). Similar species: Stenamma ignotum , Stenamma nanozoi , Stenamma picopicucha , Stenamma sandinista , Stenamma schmidti .

Geographic range.

Southern Mexico to Guatemala.

Worker description.

(17 measured) HL 0.57-0.76 (0.61), HW 0.51-0.68 (0.57), FLD 0.14-0.19 (0.15), PCW 0.03-0.07 (0.03), SL 0.46-0.64 (0.50), EL 0.09-0.11 (0.09), ACL 0.45-0.59 (0.49), ML 0.68-1.00 (0.78), PrW 0.36-0.49 (0.40), PSL 0.08-0.14 (0.11), SDL 0.06-0.11 (0.09), PL 0.26-0.40 (0.31), PH 0.16-0.23 (0.19), PW 0.14-0.19 (0.16), PPL 0.12-0.22 (0.15), PPH 0.13-0.21 (0.16), PPW 0.16-0.22 (0.18), MFL 0.50-0.72 (0.55), MTL 0.41-0.57 (0.45), CI 86-92 (92), SI 88-97 (89), REL 15-19 (16), FLI 25-29 (26), PSI 1.1-1.4 (1.3), MFI 93-104 (103), ACI1 65-69 (67), ACI2 92-99 (97).

Small- to medium-sized species; general body color dark red-brown (almost black) to brown, with appendages lighter, brown to yellow-brown toward extremities; setae golden; mandible with 6-7 teeth (usually 7), consisting of 3 larger, more distinct apical teeth, a basal tooth, and 2-3 smaller denticulate teeth, which are usually more worn, and sometimes indistinct; basal margin of mandible straight, without a basal notch or depression; mandible mostly smooth, except for scattered piligerous punctae, and a few basal striae; anterior clypeal margin entire, or at most with a nearly imperceptible median notch, only visible from anterodorsal view; median lobe of clypeus with faint longitudinal carinulae and some punctations, apex of lobe with a few short transverse carinulae, remainder of clypeus mostly smooth; posterior extension of clypeus between antennal insertions of moderate width (PCW 0.03-0.07), with sides subparallel to slightly hour-glass-shaped; frontal lobes of moderate width (FLD 0.14-0.19, FLI 25-29), not obscuring torular lobes in full-face view; head roughly oval-shaped (CI 86-92), posterior margin slightly depressed medially; eye of small to moderate size (EL 0.09-0.11, REL 15-19), oval-shaped, with 4-7 ommatidia at greatest diameter; face densely sculptured, mostly rugoreticulate, with a few longitudinal rugae along midline near frontal lobes; scape of moderate length (SI 88-97), almost reaching posterior margin of head when laid back; scape surface mostly smooth, with scattered piligerous punctae; flagellum with a distinct 4-segmented antennal club; most of mesosoma densely sculptured, dorsum of promesonotum rugoreticulate, or with irregular longitudinal rugae that only sometimes merge, side of pronotum variably rugulose-punctate, sometimes with a large patch of smooth cuticle, mesopleuron mostly punctate, with a few rugulae, side of propodeum rugulose-punctate, propodeal dorsum and upper half of declivity with a few transverse carinulae; promesonotum in profile low-domed, roughly symmetrical, sometimes dorsum slightly flattened; metanotal groove well-demarcated, moderate; propodeal spines tuberculate, often forming somewhat broad triangles (PSL 0.08-0.14, PSI 1.1-1.4); petiole appearing of moderate length (PL/HW 0.50-0.59), peduncle usually somewhat slender; petiolar node of moderate height to somewhat small (PH/PL 0.54-0.65), dorsum broadly rounded, and always pointing distinctly posteriad, area underneath node usually with a small concavity, or notch; postpetiole in profile subspherical to oblong, appearing slightly compressed anteroposteriorly; anterior faces of petiolar and postpetiolar nodes smooth, remaining surfaces mostly punctate, with a few rugulae on posterior half of postpetiole; gaster smooth, with scattered piligerous punctae; face with a mostly uniform layer of short decumbent setae; remainder of body dorsum with longer suberect setae; pilosity on gastral tergites indistinctly bilayered, with a relatively sparse layer of longer suberect to subdecumbent setae, and a sparser layer of decumbent to appressed setae; setae on scapes and legs mostly decumbent to appressed, with some suberect setae on femoral venters and coxae.

Queen description.

(5 measured) HL 0.61-0.76 (0.61), HW 0.56-0.70 (0.57), FLD 0.15-0.21 (0.16), PCW 0.04-0.08 (0.04), SL 0.50-0.64 (0.50), EL 0.15-0.20 (0.15), ACL 0.48-0.61 (0.49), ML 0.84-1.11 (0.86), PrW 0.49-0.63 (0.49), PSL 0.11-0.16 (0.14), SDL 0.09-0.12 (0.10), PL 0.33-0.44 (0.34), PH 0.19-0.25 (0.19), PW 0.17-0.22 (0.18), PPL 0.15-0.22 (0.18), PPH 0.19-0.25 (0.19), PPW 0.18-0.27 (0.21), MFL 0.55-0.73 (0.55), MTL 0.45-0.58 (0.45), CI 89-94 (94), SI 86-96 (86), REL 26-28 (26), FLI 27-31 (27), PSI 1.3-1.4 (1.4), MFI 93-104 (104), ACI1 64-67 (66), ACI2 94-98 (98).

Same as worker except for standard queen modifications and as follows: side of pronotum rugoreticulate to transversely rugose, center of pronotum transversely carinulate; mesoscutum mostly foveolate to longitudinally rugose, usually with some smooth cuticle along midline, foveolae when present piligerous; propodeum with transverse carinulae that wrap around surface; mesopleuron mostly smooth; pilosity on gastral tergites distinctly bilayered, with a sparse layer of longer suberect to subdecumbent setae and a dense layer of decumbent setae, lower layer usually almost pubescent, but sometimes less dense and longer; wing venation as in Figure 133D.

Male.

Unknown.

Biology.

This species is known only from extracts of sifted leaf litter collected from the forest floor. It occupies a variety of wet forest habitat types (e.g. rainforest, mesophyll forest, 2° wet forest, Liquidambar forest, cloud forest, oak-pine forest) and occurs from near sea level to 2000 m. Dealate queens are commonly collected in samples, suggesting that the species may nest in the leaf litter microenvironment.

Comments.

Stenamma nonotch forms a clade with Stenamma nanozoi , Stenamma sandinista , and Stenamma schmidti and is very similar to these species (Branstetter unpublished data). However, it is the only species within the clade to have the anterior clypeal margin entire, and the basal margin of the mandible straight. This feature makes it easy to distinguish from its close relatives. Stenamma nonotch is also similar to Stenamma ignotum and Stenamma picopicucha , which both have a straight basal margin of the mandible. However, neither of these species have the anterior clypeal margin entire.

There is some variation among populations of Stenamma nonotch , with workers differing in size, sculpture, and shape of the propodeal spines and petiolar node. I split this diversity into three variant forms. The type form (Figure 131) includes all of the collections from Oaxaca, Mexico, which were collected below 700 m on the wetter side of the state. Variant 1 (Figure 132 A–C) occurs at the low-elevation locality Salto de Agua in Chiapas, Mexico. Compared to the type population, specimens are smaller, have a lighter red-brown coloration, have the propodeal spines slightly more robust and projecting dorsally, and have the petiolar node in profile somewhat anteroposteriorly compressed. Variant 2 (Figure 132 A–C) occurs at the mid-elevation locality Nahá in Chiapas, Mexico. It is smaller than the type form and has the propodeal spines noticeably reduced to sharp angles, rather than sharp, projecting tubercles. Lastly, variant 3 (Figure 132 D–F) is a high elevation version of Stenamma nonotch , occurring mainly at the locality Coapilla in Chiapas, Mexico. Compared with the type form, it is larger, has darker coloration, and has a thicker petiolar node. Also, the ventral margin of the petiolar node is flat, rather than with a small concavity. Molecular data suggest that there is significant divergence among populations, but I have not seen sympatry among forms, and some populations have intermediate phenotypes. Thus, I treat the above as intraspecific variants until more data are available.

Material examined.

MÉXICO: Chiapas: 15.1km NW Bochil, [ca. 17.0912°N, 92.9914°W], 1930m, 24 Sep 1992 (R. S. Anderson); 5km NE Coapilla, 17.17558°N, 93.15012°W, 1770m, 26 May 2008 (M. G. Branstetter); 5km NE Coapilla, 17.17602°N, 93.13293°W, 1990m, 25 May 2008 (LLAMA); Lagos de Montebello, Cinco Lagos, 16.1012°N, 91.6740°W, 1600m, 21 Jul 2007 (R. S. Anderson); Lagos de Montebello, L. Pojoj, 16.09913°N, 91.67125°W, 1510m, 21 Jul 2007 (R. S. Anderson); Nahá, 16.96426°N, 91.59234°W, 985m, 8 Jun 2008 (LLAMA); 6km SW Ocosingo, 16.8672°N, 92.0787°W, 1400m, 22 Sep 1991 (R. S. Anderson); 2km S Playón de la Gloria, 16.1385°N, 90.9015°W, 170m, 22 Jul 2007 (R. S. Anderson); 13km N Pueblo Nuevo Solistahuacán, [ca. 17.211°N, 92.964°W], 1860m, 26-27 Aug 1973 (A. F. Newton); 5km E Rayón, 17.217°N, 92.967°W, 1700m, 23 Dec 1991 (P. S. Ward); 8.9km E Rayon, 17.2000°N, 92.9163°W, 1500m, 19 Sep 1991 (R. S. Anderson); 21km SW Salto de Agua, 17.38542°N, 92.42802°W, 180m, 15 Jun 2008 (M. G. Branstetter);Oaxaca: 4.3km SW Valle Nacional, 17.74320°N, 96.32729°W, 370m, 13 Aug 2009 (L. Sáenz); 7.5km S Valle Nacional, 17.70752°N, 96.30516°W, 680m, 12 Aug 2009 (M. G. Branstetter); Veracruz: Los Tuxtlas, 10km NNW Sontecomapan, 18.583°N, 95.083°W, 200m, 20 Mar 1985 (P. S. Ward).