Stenamma manni

This species is one of the largest and most conspicuous species of Stenamma, which is probably why it was the first Middle American species to be described. As defined here, S. manni occurs from 1200–3700 m elevation, but it seems to be most common between 2000–2500 m. It occurs in wet montane forests like cloud forest, and drier, more seasonal habitats, such as oak woodland. Specimens have been collected in leaf litter samples, at bait cards, in Malaise traps, and by general searching. I have found nests in logs, in the leaf litter, under rocks, and in the ground. In Central America, S. manni is commonly found at the edge of cloud forest in logs and in the ground under logs. All Stenamma manni nests tend to be very large, with hundreds to perhaps over a thousand workers (a complete colony census has not been carried out). Nests usually have brood, alates, and a single egg-laying queen. Stenamma manni is one of the most common Stenamma species to be found at bait cards, suggesting that they are active epigeic foragers. All foragers I have observed have been solitary. (Branstetter, 2013).

Identification
Branstetter (2013) - This is a common but variable species. Integument color variable; medium- to large-sized species (see HL, ML, PrW below); lateral apex of hypostomal bridge projecting ventrally as a subquadrate to broadly rounded lobe, which is usually visible behind base of mandible in profile view (sometimes visible only in lateroventral view); propodeal spines tuberculate to short (PSL 0.09–0.19, PSI 1.0–1.6); basal margin of mandible straight; anterior clypeal margin with a single median emargination; face usually completely sculptured, mostly rugoreticulate, with some longitudinal rugulae/carinulae along midline, but sometimes face mostly smooth, with only some longitudinal carinulae; mesosoma usually mostly sculptured with carinae, rugae, rugoreticulae, or punctae, only sometimes with pronotum mostly or completely smooth; eye of moderate size (EL 0.10–0.16, REL 13–21), oval-shaped, with 5–8 ommatidia at greatest diameter; frontal lobes of moderate width (FLD 0.19–0.29, FLI 25–30); first gastral sternite and tergite sometimes punctate. Similar species: Stenamma felixi, Stenamma leptospinum, Stenamma megamanni, Stenamma muralla.

Stenamma manni should be separable from most similar species by the combination of presence of a lateral hypostomal lobe; presence of tuberculate to short propodeal spines; and large body size. However this species is highly variable, and thus difficult to characterize in a very satisfactory way. Indeed, the manni complex, with all of its different variants, is a taxonomic nightmare. Nearly every population has unique, often distinctive features, and there is no evidence of sympatry among forms. It is also common to have populations that are intermediate in phenotype between variants. Populations from drier areas, especially those from central and western Mexico, tend to be lighter in color, have more developed sculpturing, and have denser pilosity, with the lower layer of gastral pilosity often pubescent. In contrast, specimens from wet forest environments are often shinier and less sculptured and have sparser pilosity. They also tend to be darker in color, but not always.

S. megamanni occurs from Chiapas, Mexico to Nicaragua and is sympatric with S. manni at many sites. However, it is a variable species and difficult to recognize from S. manni at a large geographic scale. Within the range where both species occur, I often find two forms in sympatry. S. manni always has lighter body color (usually dark red-brown), a smaller eye (usually 5–6 ommatidia at greatest diameter), and a larger, more bulging postpetiole. Stenamma megamanni, in contrast, is always black, has a larger eye (8 or more ommatidia at greatest diameter), and usually has the postpetiole similar in size to the petiolar node. In addition, there seems to be some ecological separation between the species. Even though S. megamanni does occur at high elevation and in leaf litter, I commonly find it nesting at lower elevations in riparian areas. I have found nests both in clay banks and under rocks along streams. I have never found S. manni in these environments.

Distribution
Mexico to Nicaragua.

Distribution based on Regional Taxon Lists
Neotropical Region: El Salvador, Guatemala, Honduras, Mexico, Nicaragua.

Nomenclature

 *  manni. Stenamma manni Wheeler, W.M. 1914b: 51 (w.q.) MEXICO. Wheeler, G.C. & Wheeler, J. 1972b: 237 (l.); Branstetter, 2013: 159 (w.q.m). See also: Smith, M.R. 1962a: 35.

Worker
Branstetter (2013) - (25 measured, lectotype in parentheses) HL 0.81–1.13 (0.91), HW 0.70–1.01 (0.78), FLD 0.19–0.27 (0.23), PCW 0.05–0.08 (0.08), SL 0.68–1.04 (0.75), EL 0.10–0.16 (0.14), ACL 0.62–0.88 (0.67), ML 1.05–1.50 (1.17), PrW 0.45–0.64 (0.53), PSL 0.09–0.19 (0.12), SDL 0.08–0.14 (0.10), PL 0.36–0.54 (0.44), PH 0.21–0.32 (0.25), PW 0.17–0.25 (0.21), PPL 0.21–0.33 (0.25), PPH 0.21–0.33 (0.25), PPW 0.22–0.34 (0.26), MFL 0.77–1.28 (0.85), MTL 0.61–0.97 (0.67), CI 82–91 (86), SI 88–109 (96), REL 13–21 (18), FLI 26–30 (29), PSI 1.0–1.6 (1.2), MFI 75–100 (92), ACI1 61–66 (65), ACI2 84–93 (89).

Medium- to large-sized species; general body color highly variable, ranging from mostly black (type population), to red-brown, to brown, to yellow-brown, with appendages lighter, especially at joints and toward extremities, generally brown or orange-brown to yellow-brown; setae golden brown; mandible with 6–7 teeth (usually 6), consisting of 3 distinct apical teeth, a basal tooth, and 2–3 smaller teeth in between, which are often worn and indistinct; basal margin of mandible straight, without a basal notch or depression; mandible mostly smooth, with scattered piligerous punctae, and a variable number of longitudinal striations, mostly at base and on lateral surface; anterior clypeal margin with a shallow median emargination; median lobe of clypeus often with a pair of faint longitudinal carinulae (type population) that diverge toward anterior margin, but sometimes distinct carinulae replaced or hidden by a variable number of irregular striations, apex of lobe usually with a short transverse carinula, remainder of clypeus mostly smooth; posterior extension of clypeus between frontal lobes of moderate width (PCW 0.05–0.08), with sides subparallel; frontal lobes of moderate width (FLD 0.19–0.27, FLI 26–30), never greatly obscuring torular lobes in full-face view; lateral apex of hypostomal bridge projecting ventrally as a subquadrate to broadly rounded lobe, which is usually visible behind base of mandible in profile view (reduced in type population; sometimes visible only in lateroventral view); head usually roughly oval-shaped (type population), but sometimes slightly elongate, or more often broad, becoming slightly heart-shaped (CI 82–91), posterior margin slightly to distinctly depressed medially; eye of moderate size (EL 0.10–0.16, REL 13–21), oval-shaped, with 5–8 ommatidia at greatest diameter; face usually completely sculptured, mostly rugoreticulate (rarely completely), with some longitudinal rugulae/carinulae along midline extending from frontal lobes to posterior margin, coarseness of sculpture variable (average in type population); face rarely mostly smooth, with only some longitudinal carinulae along midline and on gena; scape usually of moderate length (type population), but sometimes relatively long and slender (SI 88–109), scape when laid back reaching and often surpassing posterior margin of head; scape surface variable, usually with scattered piligerous punctae and some carinulae (type population), but sometimes scape more smooth with carinulae reduced, or scape more robust, with carinulae coarser; flagellum with distinct 4-segmented antennal club; mesosoma sculpture highly variable, usually completely sculptured, without large patches of smooth cuticle, but sometimes pronotum mostly to completely effaced; dorsum of promesonotum carinulate (type population), rugose, or rugoreticulate (often with punctae), almost always with longitudinal orientation (some aberrant specimens with transverse orientation); side of pronotum carinulate (type population), rugulose, or punctate; mesopleuron and side of propodeum punctate to rugulose-punctate, generally with more rugulae on the propodeum; dorsum and declivity of propodeum with transverse carinulae; promesonotum in profile low-domed, and usually slightly asymmetrical, with apex shifted anterior of midpoint, and anterior face steeper than posterior face (some populations roughly symmetrical); metanotal groove usually well-demarcated, width and depth variable (average in type population); propodeal spines tuberculate to short (PSL 0.09–0.19, PSI 1.0–1.6); petiole in profile appearing average (type population) to slightly elongate (PL/HW 0.48–0.62), with peduncle usually thick and robust; petiolar node in profile usually of moderate size (PH/PL 0.51–0.66), with a broadly rounded dorsum that points vertical to slightly posteriad, rarely pointing distinctly posteriad; node sometimes somewhat compressed anteroposteriorly; posterior margin of petiole in profile sometimes distinctly bent downwards, creating a slight concavity below node; postpetiolar node in profile similar in size to petiolar node (type population) or bulging (PPH/PH 0.79–1.05, PW/PPW 0.70–0.86), shape of node subcircular to asymmetrical (slightly asymmetrical in type population); petiole and postpetiole usually mostly punctate, with anterior faces of nodes variably smooth and shiny (type population), sometimes nodes with rugulae, or rarely rugoreticulae; gaster usually smooth and shiny, within scattered piligerous punctae, but sometimes (mostly northern populations in drier habitats) first gastral tergite and sternite lightly to strongly punctate; pilosity highly variable, pilosity on gastral dorsum usually clearly bilayered, with a layer of longer suberect setae, and a layer of shorter decumbent setae, but length and density of each layer variable, lower layer sometimes very dense (almost pubescent), or somewhat sparse and more subdecumbent, causing it to blend in with upper layer, rarely upper layer very long and more dense (type population average), gastral setae never greatly strongly thickened; setae on scapes uniformly suberect to subdecumbent, never with a separate layer of longer suberect setae; setae on legs decumbent to appressed, with longer suberect setae on femoral venters and coxae.

Queen
Branstetter (2013) - (7 measured) HL 0.92–1.13 (0.98), HW 0.81–1.01 (0.87), FLD 0.23–0.30 (0.25), PCW 0.07–0.10 (0.07), SL 0.81–1.00 (0.82), EL 0.23–0.27 (0.25), ACL 0.72–0.87 (0.75), ML 1.38–1.69 (1.48), PrW 0.82–1.01 (0.82), PSL 0.15–0.29 (0.21), SDL 0.13–0.16 (0.13), PL 0.52–0.68 (0.54), PH 0.28–0.36 (0.29), PW 0.23–0.32 (0.23), PPL 0.27–0.37 (0.28), PPH 0.27–0.39 (0.27), PPW 0.31–0.42 (0.32), MFL 0.98–1.30 (0.99), MTL 0.78–1.01 (0.79), CI 87–92 (89), SI 87–105 (94), REL 26–28 (28), FLI 28–30 (29), PSI 1.1–2.1 (1.6), MFI 78–95 (87), ACI1 60–66 (63), ACI2 83–91 (91).

Same as worker except for standard queen modifications and as follows (comparing queen and worker of type population form only; queen from Rancho Somecla): pronotum with transverse carinulae; mesoscutum and scutellum longitudinally carinulate; propodeum with transverse carinulae that wrap around entire surface; katepisternum mostly smooth; lower layer of setae on gastral dorsum denser; wing venation as in photo (cell underneath stigma probably aberrant, not present in other S. manni queens).



References based on Global Ant Biodiversity Informatics

 * 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.
 * Branstetter M.G. 2013. Revision of the Middle American clade of the ant genus Stenamma Westwood (Hymenoptera, Formicidae, Myrmicinae). ZooKeys 295: 1277
 * Dattilo W. et al. 2019. MEXICO ANTS: incidence and abundance along the Nearctic-Neotropical interface. Ecology https://doi.org/10.1002/ecy.2944
 * Fernandes, P.R. XXXX. Los hormigas del suelo en Mexico: Diversidad, distribucion e importancia (Hymenoptera: Formicidae).
 * Kempf, W.W. 1972. Catalago abreviado das formigas da regiao Neotropical (Hym. Formicidae) Studia Entomologica 15(1-4).
 * Longino J. T. 2013. Ants of Nicargua. Consulted on 18 Jan 2013. https://sites.google.com/site/longinollama/reports/ants-of-nicaragua
 * Longino J. T. L., and M. G. Branstetter. 2018. The truncated bell: an enigmatic but pervasive elevational diversity pattern in Middle American ants. Ecography 41: 1-12.
 * Rojas Fernandez P. 2010. Capítulo 24. Hormigas (Insecta: Hymenoptera: Formicidae). In: Diversidad Biológica de Veracruz. Volumen Invertebrados. CONABIO-Gobierno del Estado de Veracruz.
 * Vásquez-Bolaños M. 2011. Lista de especies de hormigas (Hymenoptera: Formicidae) para México. Dugesiana 18: 95-133