Stenamma longinoi, 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 : 125-127

Stenamma longinoi sp. n. Worker: Figure 109; Map: Figure 105

Type material.

Holotype worker. MÉXICO: Chiapas, Custepec, 15.72212°N, 92.94428°W ± 30m, 1680m, 19 May 2008, mesophyll forest, under epiphytes in treefall (J. Longino, collection JTL6297) [USNM, specimen JTLC000007475]. Paratypes: same data as holotype [1w, ECOSCE, JTLC000007476], [1w, MGBPC, CASENT0603913], [1w, MCZ, CASENT0623106].

Worker diagnosis.

Integument mostly dark brown to dark red-brown; large-sized species(see HL, ML, PrW below); lateral margin of hypostomal bridge with a projecting quadrate lobe (visible behind mandible in profile); gaster, and most dorsal surfaces, with a layer of thickened suberect to subdecumbent setae, gaster also with sparse layer of thinner appressed setae; mesosoma, waist, and head densely punctate (punctae fainter on head); head and mesosoma with fine rugulae and rugoreticulae, which on the mesosoma merge into the punctae, making them less obvious; eye relatively small (EL 0.13-0.16, REL 13-15), oval-shaped, with 6-7 ommatidia at greatest diameter; anterior clypeal margin with a shallow median emargination; basal margin of mandible straight to slightly sinuous, without a basal notch or depression; propodeal spines short (PSL 0.16-0.19, PSI 1.4-1.6), frontal lobes narrow (FLD 0.24-0.27, FLI 26), not obscuring torular lobes in full-face view. Similar species: Stenamma leptospinum , Stenamma manni , Stenamma muralla .

Geographic range.

Southern Mexico.

Worker description.

(4 measured) HL 1.02-1.13 (1.12), HW 0.92-1.05 (1.01), FLD 0.24-0.27 (0.26), PCW 0.05-0.08 (0.08), SL 0.79-0.85 (0.83), EL 0.13-0.16 (0.13), ACL 0.67-0.74 (0.74), ML 1.29-1.41 (1.36), PSL 0.16-0.19 (0.17), SDL 0.10-0.13 (0.10), PrW 0.57-0.64 (0.61), PL 0.46-0.49 (0.49), PH 0.29-0.32 (0.30), PW 0.22-0.25 (0.24), PPL 0.27-0.30 (0.30), PPH 0.26-0.30 (0.29), PPW 0.28-0.31 (0.30), MFL 0.93-1.03 (1.02), MTL 0.57-0.80 (0.57), CI 91-93 (91), SI 81-88 (82), REL 13-15 (13), FLI 26 (26), PSI 1.4-1.6 (1.6), MFI 99-102 (99), ACI1 64-66 (64), ACI2 84-89 (89).

Large species; general body color dark brown (almost black) to dark red-brown, with appendages and some parts of the gaster lighter brown; setae a rich golden brown; mandible with 6 teeth, middle 2 teeth near basal tooth sometimes worn and indistinct; basal margin of mandible straight to slightly sinuous, without a basal notch or significant depression; mandible mostly smooth and shining with scattered piligerous punctae and striae; anterior clypeal margin with a median emargination; median lobe of clypeus with a pair of faint longitudinal carinulae that diverge anteriorly, area in between carinulae slightly depressed, apex of median lobe with a short transverse carinula, remainder of clypeus mostly smooth and shiny; posterior extension of clypeus between antennal insertions of moderate width (PCW 0.05-0.08), sides slightly hourglass-shaped; frontal lobes narrow (FLD 0.24-0.27, FLI 26), not obscuring torular lobes in full-face view; lateral margin of hypostomal bridge with a projecting quadrate lobe (visible behind mandible in profile); head robust, somewhat heart-shaped (CI 91-93), with posterior margin broadly depressed medially; eye relatively small compared to HW (REL 13-15), but appearing of moderate size (EL 0.13-0.16), with 6-7 ommatidia at greatest diameter, oval-shaped; face densely sculptured with longitudinal carinulae and rugulae, becoming rugoreticulae toward lateral margins, interstitial areas noticeably punctate; scape relatively short (SI 81-88), not reaching posterior margin of head when laid back; scape surface with scattered carinulae and faint piligerous punctae; flagellum with a somewhat indistinct 4-segmented antennal club; mesosoma densely punctate, and with fine rugulae that merge into surrounding punctae; rugulae on anterior half of pronotal dorsum transversely arcuate across surface; rugulae on remainder of promesonotal dorsum longitudinal in orientation; pronotal side completely punctate; rugulae on mesopleuron somewhat reticulate; part of propodeal dorsum and declivity with transverse carinulae; promesonotum in profile low-domed and asymmetrical, with apex occurring anterior of midpoint; metanotal grove somewhat indistinct with anterior margin merging smoothly with promesonotal declivity; propodeal spines well-developed, short (PSL 0.16-0.19, PSI 1.4-1.6); petiole of moderate length and robust (PL/HW 0.47-0.50), node of moderate height (PH/PL 0.62-0.65), broadly domed, and pointing slightly posteriad; postpetiole in profile nearly symmetrical, somewhat bulging, about as high as petiolar node (PPH/PH 0.90-0.96); petiole and postpetiole completely punctate and with a few rugulae on posterior sides of nodes; gaster mostly smooth and shiny, with scattered piligerous punctae; much of dorsal body surface with a layer of stout standing setae; setae on scape thin, dense, and decumbent (almost pubescent); gaster with a short layer of thickened suberect to subdecumbent setae and a very sparse layer of thinner appressed setae; setae on legs mostly appressed, with a few suberect setae on the coxae and femoral venters.

Queen.

Unknown.

Male.

Unknown.

Biology.

This species is known from a single collection event made in mesophyll forest at 1680 m elevation. A few workers were found under epiphytes in a treefall. Over 100 leaf litter samples were collected from the same site and no additional specimens were retrieved. Consequently, this species is likely to be arboreal in its habits.

Comments.

Stenamma longinoi is similar to Stenamma leptospinum , Stenamma manni , and Stenamma muralla , mainly because all share the lateral hypostomal lobe. However, Stenamma longinoi is very distinct and should be easily separated from these other species by its punctate sculpture and thickened setae. Given the diversity of Stenamma manni variants (see Stenamma manni below), I do find it possible that Stenamma longinoi is an arboreal version of Stenamma manni . However, molecular data place Stenamma longinoi firmly outside of the clade that includes Stenamma manni and variants of Stenamma manni that are from all over Mexico and Central America (Branstetter unpublished data). Furthermore, Stenamma longinoi was collected in sympatry with Stenamma manni and no intermediates were found.

Material examined.

Known only from the type locality.