Temnothorax fuscatus

Wheeler (1931) reported this species was observed nesting in hollow twigs of trees or shrubs.

Identification
Prebus (2021) – A member of the fuscatus group of the Temnothorax salvini clade. Temnothorax fuscatus can be separated from all other species in the salvini clade by the following character combination: antennal scapes short: failing to reach the posterior margin of the head by about the maximum width of the antennal scape (SI 83-93); body elongate (WLI >150); metanotal groove not strongly impressed; propodeal spines very long and acute, about one and a half times as long as the propodeal declivity (PSI 23-35); propodeal spines curved and directed posteriorly or posterodorsally, never directly upward; hind femora variable, but usually strongly incrassate (FI >300); petiolar node low, elongate and rounded dorsally (NI 177-246); postpetiole narrow: greater than one and a half times as wide as the petiole in dorsal view, but less than twice as wide (PWI 165-193); setae on head, mesosoma, waist segments and gaster erect, moderately long, sparse and blunt (never long and tapering); integument variably colored, but always uniform (never bicolored).

This species displays a high degree of morphological variability (see worker and queen images, figures 109 and 110, below in the caste section); as our understanding of the geographic distribution of this variability improves, it may be revealed as a species complex. Typically, T. fuscatus is darkly colored, coarsely sculptured, and bears acute propodeal spines (see worker images, figures 109 a-i, below in the caste section). However, a nearly uniformly light colored morph is present near the southern end of its range, in Nicaragua and Costa Rica (see worker images, figures 109 j-l, below in the caste section). While costulae are present on the mesosoma of all specimens that I have examined, the degree of coarseness shows constant variability, and while some specimens bear smooth, glossy integument between the rugae, many show some degree of fine, areolate sculpture in addition (see worker images, figures 109 a,d,g,j, below in the caste section). The propodeal spines, while always fairly long, vary from the typical strongly curved form to a posterodorsally directed, nearly straight and acute form (compare the following images in the caste section below: figure 109 b vs. 109 e, h). The gynes are morphologically variable as well: for example, the lateral faces of the pronotum and procoxae are concave in some specimens, as if they are excavated to accommodate the retracted profemora (see worker image 110 b in the caste section below), but apparently this is not the rule (see worker images, figures 108 e and 110 e, below in the caste section).

Similar species: Temnothorax acutispinosus, Temnothorax subditivus, Temnothorax tenuisculptus, Temnothorax tuxtlanus, species of the annexus, augusti, fuscatus, and salvini groups. Temnothorax fuscatus can be distinguished from T. tuxtlanus by the incrassate femora (FI < 280 in T. tuxtlanus). The low, elongate petiolar node (NI >180) will separate T. fuscatus from all species listed above, aside from the salvini group and most other members of the fuscatus group. The blunt-tipped setae and short antennal scapes, which fail to reach the posterior margin of the head, will separate T. fuscatus from the species of the salvini group, which have long, tapering setae and scapes that surpass the posterior margin of the head by at least one times the maximum width of the antennal scape (SI 83-89 vs. >95). The long propodeal spines, which are longer than the propodeal declivity, as well as the uniformly colored integument, will distinguish T. fuscatus from Temnothorax ocarinae and Temnothorax skwarrae, which have very short propodeal spines and are bicolored. The acute propodeal spines will distinguish T. fuscatus from Temnothorax nebliselva, which has truncate propodeal spines.

Temnothorax fuscatus most closely resembles T. nebliselva from Costa Rica, which has a moderately depressed propodeum, mesosomal integument that is smooth and shining between the costulae, and downwardly curved, blunt or truncated propodeal spines. Temnothorax ocarinae and Temnothorax skwarrae, from Western Mexico (Jalisco state) and south-central Mexico respectively, are other apparently close relatives, based on their morphological affinities.

Distribution
Prebus (2021) - Temnothorax fuscatus is broadly distributed across mid-to-high elevation cloud forest habitats in Central America south of the Isthmus of Tehuantepec to Costa Rica.

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

Biology
Prebus (2021) - All nest collections of T. fuscatus have been taken from dead vegetation, often on live trees. Canopy fogging has yielded many specimens as well. Collection labels show that Temnothorax fuscatus has an affinity for mid-to-high elevation cloud-forest habitats.

Worker
Prebus 2021, Figure 109 a-c, worker variant Chiapas, Mexico.

Queen
Prebus 2021, Figure 108 d-g.

Male
Prebus 2021, Figure 108 h-k.

Nomenclature

 *  fuscatus. Macromischa (Macromischa) fuscata Mann, 1920: 420 (w.) GUATEMALA. Combination in Leptothorax: Baroni Urbani, 1978b: 442; in Temnothorax: Bolton, 2003: 271.

Description
Prebus (2021) - This species displays a high degree of morphological variability (Fig. 109 & Fig. 110); as our understanding of the geographic distribution of this variability improves, it may be revealed as a species complex.

Worker
Prebus (2021) - (n = 17): SL = 0.544-0.652 (0.605); FRS = 0.245-0.282 (0.264); CW = 0.699-0.810 (0.761); CWb = 0.644-0.749 (0.696); PoOC = 0.286-0.373 (0.325); CL = 0.731-0.889 (0.819); EL = 0.176-0.214 (0.196); EW = 0.124-0.156 (0.141); MD = 0.166-0.231 (0.186); WL = 1.006-1.239 (1.132); SPST = 0.251-0.380 (0.322); MPST = 0.294-0.363 (0.321); PEL = 0.363-0.459 (0.424); NOL = 0.234-0.324 (0.277); NOH = 0.121-0.147 (0.134); PEH = 0.212-0.255 (0.235); PPL = 0.200-0.274 (0.236); PPH = 0.209-0.261 (0.242); PW = 0.431-0.531 (0.489); SBPA = 0.127-0.198 (0.170); SPTI = 0.233-0.316 (0.270); PEW = 0.141-0.170 (0.157); PNW = 0.153-0.228 (0.184); PPW = 0.246-0.312 (0.278); HFL = 0.715-0.856 (0.788); HFWmax = 0.140-0.197 (0.172); HFWmin = 0.044-0.077 (0.055); CS = 1.010-1.194 (1.105); ES = 0.239-0.292 (0.266); SI = 83-93 (87); OI = 22-26 (24); CI = 80-90 (85); WLI = 154-177 (163); SBI = 20-28 (24); PSI = 23-35 (29); PWI = 165-193 (177); PLI = 163-200 (180); NI = 177-246 (208); PNWI = 105-136 (117); NLI = 58-72 (65); FI = 231-407 (317).

In full-face view, head subquadrate, longer than broad (CI 80-90). Mandibles densely, finely striate but shining and armed with five teeth: the apical-most well developed and acute, followed by a less developed preapical tooth and three equally developed smaller teeth. Anterior clypeal margin flat medially. Antennal scapes short: when fully retracted, failing to reach the posterior margin of the head capsule by about the maximum width of the antennal scape (SI 83-93). Antennae 12-segmented; antennal club of composed of three segments, with the apical-most segment as long as the preceding two in combination. Frontal carinae moderately long, extending past the antennal toruli by about two and a half times the maximum width of the antennal scape. Compound eyes weakly protruding past the lateral margins of the head capsule. Lateral margin of head weakly convex, forming a continuous arc from the mandibular insertions to the posterior margin of the head. Posterior head margin flat but rounding evenly into the lateral margins.

In profile view, compound eyes ovular and moderately large (OI 22-26), with 11 ommatidia in longest row. Pronotal declivity indistinct, neck and anterior face of pronotum forming a ~120° angle. Mesosoma slightly sinuate: very weakly convex from where it joins the pronotal neck to the propodeum, nearly flat; propodeum weakly depressed and rounds evenly into the base of the propodeal spines. Promesonotal suture extending from the posterior margin of the procoxal insertion to the mesothoracic spiracle, which is moderately well developed. Metanotal groove visible as a disruption of the sculpture laterally from where it arises between the mid- and hind coxae to where it ends in the poorly developed metathoracic spiracle, which is nearly indistinguishable from the ground sculpture. Propodeal spiracle moderately well developed, directed posterolaterally, and separated from the propodeal declivity by about five spiracle diameters. Propodeal spines well developed and very long (PSI 23-35), about one and a half times as long as the propodeal declivity, tapering evenly from the base, evenly downcurved, and acute. Propodeal declivity weakly concave, forming a rounded ~110° angle with the base of the propodeal spines. Propodeal lobes rounded and weakly developed. Metapleural gland bulla very large, extending from the metacoxal insertion three quarters of the way to the propodeal spiracle. Petiole moderately long (PLI 163-200), without tubercles anterodorsally. Subpetiolar process in the form of a moderately large, anteriorly curved, blunt tooth; ventral margin of petiole slightly bulging medially. Petiolar peduncle moderately long: comprising about half the length of the petiole. Petiolar node low and dorsally rounded: transition between peduncle and node very subtly marked by a rounded angle of ~150°, resulting in a weakly concave anterior node face; anterior face rounding evenly into dorsal and posterior faces. Postpetiole long; evenly rounded anteriorly, weakly convex dorsally, and lobed ventrally.

In dorsal view, humeri developed and distinct: evenly rounded and wider than the rest of the mesosoma; mesothoracic spiracles weakly protruding past the lateral margins of the mesosoma, visible as slight angles where the pronotum meets the mesonotum. Promesonotal suture visible as a disruption in the sculpture. Mesometanotal suture visible as a very weak sulcus. Propodeum depressed posterior to the metanotal groove, which is also represented by a very weak sulcus and disruption in the ground sculpture. Propodeal spines closely approximated basally and diverging apically, their apices separated from each other by about their length, the negative space between them "U" shaped. Petiolar peduncle with spiracles very weakly protruding past the lateral margins, and slightly constricted anterior to them. Petiolar node evenly ovular and slightly longitudinally elongate; node broader than the peduncle and evenly grading into the caudal cylinder, which is slightly narrower than the node. Postpetiole narrow (PWI 165-193) longitudinally elongate, and campaniform. Anterior margin of the postpetiole flat and evenly rounds into the lateral margins, which weakly diverge to the angulate posterior corners; posterior margin flat. Metafemur very incrassate (FI 231-407).

Sculpture: median clypeal carina present, extending posteriorly to the level of the anterior margins of the antennal insertions, and flanked on either side by two equally strong carinae. Lateral clypeal lobes with additional, weaker carinae; ground sculpture finely areolate-costulate. Antennal scapes areolate. Cephalic dorsum areolate, with costulae between the frontal carinae. Lateral surfaces of head areolate with costulae overlying the ground sculpture; costulae becoming stronger between the compound eye and the mandibular insertion. Ventral surface of the head weakly areolate. Pronotal neck areolatestrigulate. Lateral surfaces of the pronotum, mesopleurae, and lateral surface of propodeum costate, with weak areolate ground sculpture. Propodeal declivity weakly areolate, but smooth and shining between the propodeal spines. Dorsal surface of mesosoma sculptured similarly to the lateral surface. Femora weakly areolate. Petiole weakly areolate ventrally, otherwise sculptured similarly to the mesosoma. Postpetiole densely areolate, with fine costulate overlying the ground sculpture. First gastral tergite with fine areolate sculpture on the basal quarter, otherwise smooth and shining, with moderately strong spectral iridescence. First gastral sternite smooth and shining, with moderately strong spectral iridescence.

Setae: antennal scapes and funiculi with short, decumbent pilosity. Dorsum of the head, pronotum, waist segments, and gaster with sparse, erect, blunt-tipped setae, the longest of which are about the length of the compound eye. The head bears ~20, mesosoma ~18, petiole 6, postpetiole ~8, and first gastral tergite ~30 setae. Short, sparse pubescence present over the entire body, but difficult to detect against the densely sculptured integument.

Color: predominantly medium brown. Mandibles, antennae, pronotal neck, coxae, trochanters, femora, tibiae, and gastral sclerites (excluding the basalmost) testaceous. Tarsi and sting testaceous yellow.

Queen
Prebus (2021) - (n = 6): SL = 0.573-0.646 (0.619); FRS = 0.286-0.321 (0.303); CW = 0.815-0.885 (0.852); CWb = 0.733-0.815 (0.771); PoOC = 0.334-0.362 (0.350); CL = 0.858-0.924 (0.898); EL = 0.238-0.275 (0.259); EW = 0.180-0.200 (0.189); MD = 0.161-0.199 (0.177); WL = 1.597-1.793 (1.701); SPST = 0.237-0.275 (0.262); MPST = 0.395-0.445 (0.419); PEL = 0.438-0.494 (0.471); NOL = 0.291-0.343 (0.317); NOH = 0.121-0.155 (0.145); PEH = 0.245-0.310 (0.278); PPL = 0.238-0.300 (0.264); PPH = 0.297-0.377 (0.342); PW = 0.754-0.822 (0.795); SBPA = 0.259-0.387 (0.327); SPTI = 0.274-0.317 (0.297); PEW = 0.193-0.236 (0.215); PNW = 0.231-0.290 (0.264); PPW = 0.343-0.394 (0.369); HFL = 0.789-0.865 (0.836); HFWmax = 0.174-0.197 (0.187); HFWmin = 0.059-0.070 (0.064); CS = 1.162-1.275 (1.220); ES = 0.330-0.366 (0.354); SI = 78-85 (80); OI = 28-31 (29); CI = 81-90 (86); WLI = 215-230 (221); SBI = 35-51 (42); PSI = 0-16 (8); PWI = 162-182 (172); PLI = 165-197 (179); NI = 194-264 (220); PNWI = 120-128 (123); NLI = 59-73 (67); FI = 263-313 (294).

In full-face view, head subquadrate, longer than broad (CI 81-90). antennal scapes short: when fully retracted, failing to reach the posterior margin of the head capsule by about the maximum width of the antennal scape (SI 78-85). Mandibles densely striate but shining and armed with six teeth: the apical-most well developed, followed by a less developed preapical tooth and four equally developed smaller teeth. Anterior clypeal margin weakly emarginated medially. Antennae 12-segmented; antennal club composed of three segments, with the apical-most segment as long as the preceding two in combination. Frontal carinae moderately long, extending past the antennal toruli by about two and a half times the maximum width of the antennal scape. Compound eyes moderately protruding past the lateral margins of the head capsule. Lateral margin of head evenly convex, diverging from the mandibular insertions to below the compound eyes. Posterior head margin flat, rounding evenly into the lateral margins.

In profile view, compound eyes ovular and large (OI 28-31), with 17 ommatidia in longest row. Pronotum with a distinct shape: longitudinally excavate laterally. Procoxae similarly shaped, with the anterior face strongly and evenly concave. Mesoscutum rounded evenly anteriorly, not fully covering the dorsal surface of the pronotum, and flat dorsally. Mesoscutellum on the same level as the mesoscutum but sloping posteriorly. Metanotum on the same plane as the mesoscutellum. Propodeum on the same plane as the previous sclerites. Propodeal spiracle well developed, directed posterolaterally, and separated from the propodeal declivity by about five spiracle diameters. Propodeal spines absent but represented as blunt angles. Propodeal declivity slightly concave. Propodeal lobes rounded and very weakly developed. Metapleural gland bulla large, extending from the metacoxal insertion three quarters of the way to the propodeal spiracle. Petiole moderately long (PLI 165-197), without tubercles anterodorsally. Subpetiolar process in the form of a moderately large, acute tooth, which grades evenly into the ventral margin of the petiole posteriorly. Petiolar peduncle short: comprising about a quarter of the total length of the petiole. Petiolar node low and dorsally rounded: transition between peduncle and node an even grade; anterior face meeting the dorsal face at a rounded ~120° angle; dorsal face rounding evenly into the posterior face. Postpetiole weakly convex anteriorly, bulging slightly anterodorsally before flattening posterodorsally; lobed ventrally.

In dorsal view, mesoscutum not fully covering pronotum anteriorly; humeri visible laterally as angulate sclerites. Mesoscutum with a distinctive shape: hexagonal, with anterior face narrow and weakly convex, lateral faces diverging posteriorly to the wing bases, then converging slightly to the posterior face, which is broader than the anterior face. Propodeal angles diverging apically. Petiolar peduncle with spiracles weakly protruding past the lateral margins. Petiolar node, when viewed posterodorsally, with node narrowing apically and the dorsal margin weakly emarginated. Petiolar node slightly narrower than the peduncle, and evenly grading into the caudal cylinder, which slightly narrower than the node. Postpetiole narrow (PWI 162-182), and subquadrate. Anterior margin of postpetiole flat, with corners marked by rounded angles as it transitions to the lateral margins, which are parallel to the angulate posterior corners; posterior margin flat. Metafemur moderately to strongly incrassate (FI 263-313).

Sculpture: median clypeal carina present, extending from the anterior margin to the level of the antennal insertions, ground sculpture longitudinally striate. Lateral clypeal lobes with additional carinae. Antennal scapes areolate-costulate. Cephalic dorsum sculptured similarly to the worker. Lateral surfaces of head sculptured similarly to the worker, but with rugose between the compound eye and the mandibular insertion. Ventral surface of head with weakly longitudinally areolate-costulate sculpture, which becomes weaker medially. Pronotal neck areolate-strigulate. Pronotum weakly areolate-costulate anteriorly, lateral faces smooth and shining through weak costulate sculpture. Anepisternum and katepisternum shining on their anterior quarters, transitioning into areolate-costulate sculpture posteriorly. Metapleuron strongly costulate, with weak areolate ground sculpture. Propodeal declivity smooth and shining. Mesoscutum costulate, with a small patch of smooth and shining sculpture anteromedially. Mesoscutellum costulate. Metanotum smooth and shining. Dorsum of propodeum coarsely costulate over areolate ground sculpture. Femora smooth and shining, with traces of weak areolate sculpture. Petiole shining and very weakly areolate ventrally; dorsum of peduncle and node smooth and shining. Dorsolateral face of petiole coarsely costulate over weak areolate sculpture. Postpetiole finely costulate, overlying areolate sculpture laterally and on the posterior quarter. First gastral tergite and sternite smooth and shining, with moderately strong spectral iridescence.

Setae: antennal scapes and funiculi with short, decumbent pilosity. Dorsum of the head, pronotum, waist segments, and gaster with sparse, erect, blunt-tipped setae, the longest of which are about half the length of the compound eye. Short, sparse pubescence present over the entire body, but difficult to detect against the densely sculptured integument.

Color: predominantly medium brown. Mandibles, antennae, pronotal neck, coxae, trochanters, femora, tibiae, and gastral sclerites (excluding the basalmost) testaceous. Wing bases, tarsi and sting testaceous yellow.

Male
Prebus (2021) - (n = 1): SL = 0.255; FRS = 0.158; CW = 0.593; CWb = 0.476; PoOC = 0.226; CL = 0.554; EL = 0.241; EW = 0.192; MD = 0.049; WL = 0.936; SPST = n/a; MPST = 0.265; PEL = 0.328; NOL = 0.226; NOH = 0.096; PEH = 0.191; PPL = 0.211; PPH = 0.167; PW = 0.589; SBPA = n/a; SPTI = n/a; PEW = 0.145; PNW = 0.196; PPW = 0.239; HFL = 0.631; HFWmax = 0.119; HFWmin = 0.055; CS = 0.753; ES = 0.337; SI = 54; OI = 45; CI = 86; WLI = 197; SBI = n/a; PSI = n/a; PWI = 165; PLI = 155; NI = 235; PNWI = 135; NLI = 69; FI = 216.

In full-face view, head subovate, longer than broad (CI 86). Mandibles smooth and shining, with traces of striae and armed with five teeth: the apical-most well developed, followed by a smaller preapical tooth and three roughly equally developed smaller teeth. Anterior clypeal margin weakly emarginate. Antennal scapes short: when fully retracted, failing to reach the posterior margin of the head capsule by about three times the maximum width of the antennal scape (SI 54). Antennae 13-segmented; antennal club composed of four segments, with the apical-most segment slightly longer than the preceding three in combination. Frontal carinae short, extending past the antennal toruli by one and a half times the maximum width of the antennal scape. Compound eyes strongly protruding past the lateral margins of the head capsule. Posterior head margin flat, rounding evenly into the lateral margins. Lateral margin of head convex behind the compound eyes, margin between the mandibular insertions and the anterior margin of the compound eye straight.

In profile view, anterior of head concave. Compound eyes ovular and large (OI 45), with 19 ommatidia in the longest row. Mesoscutum bulging anteriorly, covering the dorsal surface of the pronotum, and flat dorsally. Mesoscutellum on the same plane as the mesoscutum; dorsum evenly rounding into the posterior margin. Metanotum extending past the posterior margin of the mesoscutellum. Propodeal spiracle well developed, directed laterally, and separated from the propodeal declivity by about four spiracle diameters. Propodeal spines absent, indicated by weak, rounded angles on the dorsum of the propodeum. Propodeal lobes rounded and weakly developed. Metapleural gland bulla very large, extending three quarters of the way between the insertion of the metacoxa and the propodeal spiracle. Petiole moderately long (PLI 155), without tubercles anterodorsally. Subpetiolar process absent. Petiolar peduncle short: comprising less than a quarter of the total length of the petiole. Petiolar node low and rounded, the convergence of the anterior and posterodorsal faces marked by a rounded angle. Postpetiole evenly rounded anterodorsally, before flattening posteriorly; ventral surface concave.

In dorsal view, mesoscutum covering pronotum anteriorly, humeri not visible laterally. Petiolar peduncle with spiracles slightly protruding past the lateral margins. Petiolar node wider than the peduncle and the caudal cylinder. Postpetiole narrow (PWI 165), elongate, and campaniform. Anterior margin of postpetiole weakly convex, with the anterior corners evenly rounding into the lateral margins, which evenly diverge to the angulate posterior corners; posterior margin of postpetiole flat. Metafemur not incrassate (FI 216).

Sculpture: median clypeal carina absent. Antennal scapes shining through very weak areolate sculpture. Head areolate, with a smooth and shining central strip extending from the frontal triangle to the median ocellus. Area around the antennal insertions also smooth and shining. Lateral surface of head areolate. Ventral surface of head weakly areolate-costulate. Pronotal neck weakly areolate. Lateral surfaces of pronotum, anepisternum, katepisternum, and metapleuron smooth and shining, but katepisternum has traces of areolate sculpture. Propodeum weakly areolate laterally; propodeal declivity smooth and shining. Dorsally, mesoscutum weakly longitudinally areolate-costulate, with smooth and shining patches anteromedially and anterolaterally. Mesoscutellum smooth and shining. Femora smooth and shining. Petiole with shallow areolate sculpture ventrally, the dorsal surface of the node smooth and shining; dorsum of peduncle and dorsolateral faces of node areolate with overlying costulate sculpture. Dorsal surface of postpetiole smooth and shining. First gastral tergite and sternite smooth and shining.

Setae: antennal scapes and funiculi with short, decumbent pilosity. Dorsum of the head, pronotum, waist segments, and gaster with sparse, erect, tapering setae, the longest of which are about half the length of the compound eye. Short, sparse pubescence present over the entire body, but difficult to detect against the sculptured integument.

Color: predominantly medium brown. Mandibles, antennae, pronotum, legs, wing bases, and genitals light yellow.

Type Material
Prebus (2021) - Syntype workers. Antigua, Guatemala. One syntype here designated lectotype.

Lectotype worker: GUATEMALA: Sacatepéquez: Antigua, 21 December 1911, Wm. M. Wheeler, 1 worker (USNMENT00529240).

Paralectotype workers: same data as lectotype: 3 workers, top worker with head missing (USNMENT00921897) [USNM].

Etymology
Prebus (2021) - Morphological, Latin 'fuscatus' (= darkened), presumably for the dark integument of the type series.

References based on Global Ant Biodiversity Informatics

 * Kempf, W.W. 1972. Catalago abreviado das formigas da regiao Neotropical (Hym. Formicidae) Studia Entomologica 15(1-4).