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Species: Stenamma maximon   Branstetter, 2013 

Classification:
Download Data

Taxonomic History (provided by Barry Bolton, 2020)

Stenamma maximon Branstetter, 2013 PDF: 172, figs. 115-118 (w.q.) GUATEMALA. Neotropic. AntCat AntWiki

Overview:

This species belongs to the Middle American clade of Stenamma (see Branstetter 2012). All content on this page modified from Branstetter (2013) unless noted otherwise.

// Distribution

Distribution:

  Geographic regions (According to curated Geolocale/Taxon lists):
    Americas: El Salvador, Guatemala, Honduras, Mexico
  Biogeographic regions (According to curated Bioregion/Taxon lists):
    Neotropical

Distribution Notes:

Southern Mexico to Honduras. No records from Belize.

Biology:

Stenamma maximon is an inhabitant of high elevation wet forest habitats (e.g. cloud forest, wet oak forest, hardwood forest, wet oak-pine forest), ranging from approximately 1700–2800 m elevation. When present, S. maximon workers are one of the most common components of the leaf-litter microenvironment, with most collections of the species made by sifting leaf litter from the forest floor. It has been collected also fairly commonly at cookie baits, suggesting that workers do forage epigeically some of the time. This is not surprising since S. maximon is a larger species of Stenamma. Branstetter (2013) found only one nest of S. maximon, which was in a small log in leaf litter. A few stray workers have been collected also from underneath a rock. Given these observations, it is likely that S. maximon nests in wood in the leaf litter and forages both within the leaf litter and sometimes above it.

Identification:

Worker diagnosis. Integument mostly black, or dark brown to brown; medium- sized species (see HL, ML, PrW below); basal margin of mandible usually sinuous, with a distinct basal depression, but without a basal tooth (rarely basal margin appearing nearly straight); anterior clypeal margin undulating, with 2–4 distinct to somewhat blunt teeth; face sculpture variable, usually mostly smooth and shiny, with, at most, faint carinulae extending to about ¾ the distance to posterior margin of head, but some populations with face mostly rugoreticulate, with only area around posterior margin becoming smooth; pronotum sculpture variable, usually mostly smooth and shiny, but sometimes with some longitudinal rugulae on humeri, remainder of mesosoma with rugulae and punctae; postpetiole bulging, appearing distinctly larger than petiolar node (PPH/PH 0.96–1.14; PW/PPW 0.65–0.78); eye of moderate size (EL 0.11–0.16, REL 16–22), oval-shaped, with 6–8 ommatidia at greatest diameter (rarely 9 or 10); propodeal spines usually tuberculate, or at least forming a sharp angle, but sometimes forming a blunt angle, or becoming more developed, short (PSL 0.07–0.12, PSI 1.0–2.0).

Similar species: Stenamma crypticum, S. huachucanum, S. ochrocnemis.

     Worker description. (23 measured) HL 0.67–0.86 (0.79), HW 0.57–0.76 (0.68), FLD 0.16–0.21 (0.19), PCW 0.02–0.0.05 (0.04), SL 0.53–0.74 (0.68), EL 0.11–0.16 (0.12), ACL 0.49–0.65 (0.59), ML 0.84–1.09 (1.02), PrW 0.39–0.50 (0.46), PSL 0.07–0.12, SDL 0.06–0.09, PL 0.29–0.38 (0.37), PH 0.19–0.24 (0.23), PW 0.15– 0.19 (0.18), PPL 0.21–0.27 (0.24), PPH 0.20–0.25 (0.25), PPW 0.22–0.27 (0.26), MFL 0.57–0.82 (0.76), MTL 0.48–0.65 (0.61), CI 83–93 (85), SI 80–101 (100), REL 16–22 (18), FLI 25–30 (28), PSI 1.0–2.0 (1.1), MFI 89–108 (89), ACI1 66–70 (68), ACI2 85–96 (88).
     Medium-sized species; general body color mostly black, or dark brown to brown, with appendages dark brown to orange-brown, lighter at joints and toward extremities; setae golden brown; mandible with 6–8 teeth (usually 7), consisting of 3 distinct apical teeth, a basal tooth, and 2–4 smaller teeth/denticles, which are often worn and indistinct; basal margin of mandible usually sinuous, with a distinct basal depression, but without a basal tooth, sometimes basal margin only slightly sinuous or nearly straight; mandible often mostly smooth and shiny, with scattered piligerous punctae and some striations (type population), but sometimes surface completely carinulate, with carinulae extending from base to near teeth; anterior clypeal margin forming 2–4 distinct to somewhat blunt teeth, outer teeth often larger and sharper than inner teeth (best viewed in anterodorsal view); median clypeal lobe with a pair of faint longitudinal carinulae, apex of lobe with a short transverse carinula, remainder of clypeus mostly smooth and shiny; area in between median lobe of clypeus and anterior clypeal margin forming a distinct cavity where mandibles insert; posterior extension of clypeus between antennal insertions of moderate width (PCW 0.02–0.0.05), with sides subparallel to slightly hour-glass-shaped; frontal lobes of moderate width (FLD 0.16– 0.21, FLI 25–30), not greatly covering torular lobes in full-face view; head roughly oval-shaped (CI 83–93), with posterior margin flat to slightly depressed mesad; face sculpture variable, usually mostly smooth and shiny (type population), with, at most, faint carinulae extending to about ¾ the distance to posterior margin of head, but some populations with face mostly rugoreticulate, with only area around posterior margin becoming smooth; scape of moderate length (SI 80–101), reaching posterior margin of head when laid back; scape surface mostly smooth and shiny, with scattered piligerous punctae; flagellum with a distinct 4-segmented antennal club; pronotum and mesonotal dorsum sculpture variable, usually mostly smooth and shiny, but sometimes with longitudinal rugulae on humeri, remainder of mesosoma mostly sculptured (contrast between smooth pronotum, and sculptured mesonotum, mesopleuron, and propodeum distinctive); mesopleuron mostly punctate, with a few rugulae; side of propodeum with rugulae and some faint punctae; dorsum and declivity of propodeum with variable number of transverse carinulae; promesonotum in profile low-domed, and roughly symmetrical, but anterior declivity sometimes more sharply angled than posterior face (type population); metanotal groove in profile well-demarcated, anterior slope often smoothly transitioning with promesonotum; propodeal spines usually tuberculate (type population), or at least forming sharp angles, but sometimes forming blunt angles, or more developed and short (PSL 0.07–0.12, PSI 1.0–2.0); petiole of moderate length (PL/HW 0.46–0.56), with peduncle thick, often with anteroventral edge sharp; petiolar node in profile somewhat small (PH/PL 0.58–0.68), wedge-shaped, with anterior face longer and more sloping than almost vertical posterior face, dorsum of node rounded, and distinctly pointed posteriad; postpetiole bulging, globular, appearing distinctly larger than petiolar node (PPH/PH 0.96–1.14; PW/ PPW 0.65–0.78), anterior face of node much longer than posterior face; petiolar and postpetiolar nodes mostly smooth and shiny, remaining waist surfaces punctate, with a few rugulae around bases of nodes; gaster smooth and shiny, with scattered piligerous punctae; pilosity on face short, with a layer of sparse suberect setae, and a denser layer of decumbent setae, remainder of body dorsum with longer standing pilosity; pilosity on gastral dorsum usually distinctly bilayered, with a layer of longer suberect to subdecumbent setae, and a layer of shorter decumbent setae, both layers similar in density; setae on scape and legs mostly decumbent to appressed, with some longer suberect setae on femoral venters and coxae.
     Queen description. (10 measured) HL 0.73–0.84 (0.84), HW 0.67–0.76 (0.76), FLD 0.19–0.23 (0.23), PCW 0.03–0.06 (0.06), SL 0.57–0.71 (0.71), EL 0.19–0.22 (0.22), ACL 0.47–0.62 (0.62), ML 1.05–1.34 (1.34), PrW 0.56–0.74 (0.74), PSL 0.13–0.17 (0.14), SDL 0.09–0.10 (0.10), PL 0.37–0.47 (0.47), PH 0.23–0.27 (0.27), PW 0.19–0.22 (0.22), PPL 0.20–0.29 (0.27), PPH 0.24–0.30 (0.30), PPW 0.27– 0.33 (0.33), MFL 0.63–0.84 (0.84), MTL 0.55–0.70 (0.70), CI 91–93 (91), SI 82–94 (94), REL 26–30 (29), FLI 27–30 (30), PSI 1.4–1.7 (1.4), MFI 90–108 (90), ACI1 64–68 (65), ACI2 76–93 (87).
     Same as worker except for standard queen modifications and as follows (comparison between worker and queen of type population form only): facial sculpture usually more developed (carinulae/rugulae longer and more distinct); mesopleuron mostly smooth and shiny; propodeum with transverse carinulae that wrap around entire surface; lower layer of gastral setae more dense, almost pubescent; propodeal spines (compared to worker from same population) slightly longer, more developed (PSL 0.13–0.17, PSI 1.4–1.7).
     Male. Unknown.

Comments:

The presence of a bulging postpetiole, a sinuous basal margin of the mandible, and a toothed anterior clypeal margin, makes S. maximon easily separable from most other Stenamma species. However, S. maximon forms a complex of phenotypic variants (described below) and some populations lose the distinctiveness of the type population form and are more difficult to separate from similar species.

Distinctive features of the type population form (CASENT0604875) are indicated in the species description (see parenthetical comments). Most notable are the characters mentioned in the previous paragraph, combined with a mostly smooth head and promesonotum. This form occurs mainly at high elevation sites in Chiapas, Mexico, and throughout most of Guatemala. It co-occurs with variant 1 at several sites in Guatemala.

Variant 1 (CASENT0605136) includes many populations in Guatemala and Honduras. Each is variable and some are intermediate in morphology between variant 1 and the type form. Variant 1 differs from the type form as follows: basal margin of mandible only slightly sinuous, without a distinct basal depression; teeth of anterior clypeal margin reduced, sometimes only two blunt middle teeth or undulations perceptible; face strongly sculptured with rugoreticulae and carinulae, only sometimes posterior ¼ of head smooth; lateral margins of promesonotal dorsum with distinctive oblique carinulae/rugulae that cross from upper portion of pronotal side to dorsum, middle of promesonotum smooth; propodeal spines reduced to blunt angles. Variant 1 (CASENT0605136) specimens have been found with the type form (CASENT0605089) most often at the locality 5km SE Antigua in Guatemala. This sympatry suggests that the two forms are somewhat reproductively isolated from one another. Variant 1 was not split out as a distinct species, however, because some populations, especially in Honduras, appear intermediate in phenotype. The general pattern observed is that the type form occurs in Chiapas, Mexico, to Guatemala; variant 1 occurs in Guatemala, often in sympatry with the type form; and then populations in Honduras appear intermediate. There is also some similarity between variant 1 and certain populations of S. crypticum, perhaps indicating that these two species occasionally hybridize.

Variant 2 (CASENT0605448) is known from a few collections made from the wet side of the Sierra Juarez Mountains in Oaxaca, Mexico. These specimens are larger than average, have short propodeal spines (longer than in type form), and have lighter brown-black body coloration.

Variant 3 (CASENT0623062) is known from a single collection at 4.6km S Suchixtepec in Oaxaca, Mexico. It is similar to variant 2, except that the basal margin of the mandible is nearly straight and the anterior clypeal margin appears as a median emargination, without teeth. It is possible this variant is not conspecific with S. maximon, but has evolved similar features due to convergence. I have not been able to test this hypothesis with molecular data, but it should be done.

The specific epithet maximon refers to the folk saint Maximón, or San Simon, who is worshipped by Mayan peoples in the highlands of western Guatemala.

Taxonomic Notes:

Type material. Holotype worker. GUATEMALA: El Progresso, Cerro Pinalón, 15.08654°N, 89.94445°W ±50m, 2550m, 30 Apr 2009, cloud forest, ex sifted leaf litter (LLAMA, collection Wa-B-01-2-02) [USNM, specimen CASENT0604875]. Paratypes: same data as holotype but 15.08753°N, 89.94446°W ±50m, 2550m, 30 Apr 2009 (LLAMA, Wa-B-01-2-38) [1w, CAS, CASENT0623344], [1w, EAPZ, CASENT0623345], [1w, ECOSCE, CASENT0623346], [1w, FMNH, CASENT0623347], [1w, ICN, CASENT0623348], [1w, INBio, CASENT0623349], [1w, JTLC, CASENT0623350], [1w, LACM, CASENT0623351], [1w, MGBPC, CASENT0623352], [1w, MCZ, CASENT0623353], [1w, MZSP, CASENT0623354], [1w, UCD, CASENT0623355], [1w, UNAM, CASENT0623356], [1w, UVGC, CASENT0623357]; 15.08350°N, 89.95319°W ±55m, 2500m, 2 May 2009 (LLAMA, Wm-B-01-2-02) [1dq, 2w, USNM, CASENT0623358, CASENT0623359, CASENT0623360].

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: 279 times found in cloud forest, 60 times found in oak forest, 53 times found in hardwood forest, 33 times found in cloud forest on ridge top, 16 times found in riparian cloud forest, 6 times found in wet oak forest, 5 times found in oak/cloud forest, 4 times found in mixed oak-cloud forest, 5 times found in disturbed cloud forest, 2 times found in Quercus mesic forest, ...

Found most commonly in these microhabitats: 426 times ex sifted leaf litter, 60 times at bait, 6 times forest litter, 2 times leaf/log litter, 3 times litter, 3 times leaf litter, 1 times sifted leaf litter, 1 times nest in log, 1 times forest litter, Berlese, 1 times under rock, 1 times ex sifted litter, ...

Collected most commonly using these methods: 322 times MiniWinkler, 71 times maxiWinkler, 22 times Berlese, 60 times Baiting, 16 times Berlese/Winkler, 33 times Hojarasca berlese, 11 times Winkler, 2 times search.

Elevations: collected from 1760 - 2750 meters, 2300 meters average

Collect Date Range: collected between 1971-05-14 and 2010-05-28

Type specimens: Holotype Stenamma maximon: casent0604875



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