Temnothorax balnearius

Known only from the type collection workers and queen, which were found in a dead agave stalk.

Identification
Prebus (2021) – A member of the annexus group of the Temnothorax salvini clade. Temnothorax balnearius can be separated from other species in the salvini clade by the following character combination: head narrow (CI 80-84); erect setae present on gula; metanotal groove absent; propodeum not depressed; propodeum bearing setae; propodeal spines moderately short, slightly shorter than the propodeal declivity (PSI 24-27); hind femora strongly incrassate (FI 357-452); petiole with short peduncle: peduncle comprising about a quarter of the total length of the petiole; petiolar node erect and subquadrate, not overhanging the caudal cylinder in profile view; postpetiole narrow (PWI 153-180); first gastral tergite smooth and shining; integument medium brown; dorsum of head, mesosoma, waist segments and gaster with erect, short, blunt-tipped setae; legs without erect setae.

Similar species: Temnothorax anaphalantus, Temnothorax andrei, Temnothorax caguatan, Temnothorax carinatus, Temnothorax cokendolpheri, Temnothorax nitens, Temnothorax pilicornis, Temnothorax pseudandrei, Temnothorax rugosus, Temnothorax subditivus, Temnothorax tenuisculptus, Temnothorax wardi, species of the silvestrii group, and other members of the annexus group. Temnothorax balnearius can be separated from all of the above species, except for T. anaphalantus, T. rugosus, T. wardi, and other members of the annexus group by the medially emarginate anterior clypeal margin. Furthermore, it can be distinguished from T. caguatan by the 12-segmented antennae, which are 11-segmented in the latter. The erect, subquadrate petiolar node of T. balnearius contrasts with the node of T. subditivus, which is squamiform, and the nodes of T. nitens, T. rugosus and T. wardi, which are cuneiform to subcuneiform. The dorsal margin of the mesosoma is continuous in T. balnearius, as opposed to sinuate, with a depressed propodeum in T. tenuisculptus. The narrow postpetiole contrasts with the very broad postpetiole of T. pilicornis and T. wardi (PWI 153-180 vs. >180). The massively incrassate hind femora will separate T. balnearius from all species listed above (except for T. subditivus, T. tenuisculptus, T. rugosus, and the annexus group), which have less incrassate hind femora (FI 357-452 in T. balnearius vs. < 300). Within the annexus group, the following characters distinguish T. balnearius from its close relatives: gular region with erect setae, as opposed to absent (Temnothorax quercicola) or present but decumbent (Temnothorax annexus); head relatively narrow (CI 80-84 vs. >85 in Temnothorax arbustus and Temnothorax obtusigaster).

Distribution
The only known specimens are from the type collection, which were found in a low elevation site in Baja California Sur.

Distribution based on Regional Taxon Lists
Neotropical Region: Mexico.

Biology
Prebus (2021) - Temnothorax balnearius is known only from one collection in the low elevations of Baja California Sur, where it was collected from a dead Agave stalk near El Charro hot springs. The vegetation of this region is dominated by xeric scrub and low tropical deciduous forest.

Nomenclature

 * . Temnothorax balnearius Prebus, 2021: 102, figs. 95C, 98 (w.dq.) MEXICO (Baja California Sur).

Worker
(n = 8): SL = 0.625-0.699 (0.668); FRS = 0.241-0.293 (0.269); CW = 0.802-0.897 (0.855); CWb = 0.713-0.807 (0.769); PoOC = 0.334-0.400 (0.363); CL = 0.860-0.996 (0.928); EL = 0.194-0.229 (0.215); EW = 0.149-0.181 (0.166); MD = 0.208-0.246 (0.229); WL = 1.120-1.312 (1.219); SPST = 0.287-0.343 (0.315); MPST = 0.331-0.416 (0.382); PEL = 0.354-0.459 (0.407); NOL = 0.182-0.261 (0.234); NOH = 0.150-0.184 (0.167); PEH = 0.279-0.337 (0.308); PPL = 0.201-0.262 (0.239); PW = 0.508-0.599 (0.550); SBPA = 0.205-0.272 (0.241); SPTI = 0.256-0.316 (0.290); PEW = 0.188-0.226 (0.208); PNW = 0.181-0.244 (0.214); PPW = 0.299-0.380 (0.344); HFL = 0.708-0.805 (0.761); HFWmax = 0.223-0.257 (0.245); HFWmin = 0.054-0.072 (0.063); CS = 1.151-1.296 (1.233); ES = 0.275-0.320 (0.298); SI = 84-91 (87); OI = 23-25 (24); CI = 80-84 (83); WLI = 156-164 (158); SBI = 29-34 (31); PSI = 24-27 (26); PWI = 153-180 (166); PLI = 158-178 (171); NI = 121-154 (140); PNWI = 93-108 (103); NLI = 51-63 (57); FI = 357-452 (393).

In full-face view, head subquadrate, longer than broad (CI 80-84). 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 emarginated medially. Antennal scapes short: when fully retracted, failing to reach the posterior margin of the head capsule by about one and a half times the maximum width of the antennal scape (SI 84-91). Antennae 12-segmented; antennal club of composed of three segments, with the apical-most segment about one and a half times as long as the preceding two in combination. Frontal carinae short, extending past the antennal toruli by about one 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 weakly convex, forming a continuous arc from the mandibular insertions to the posterior margin of the head. Posterior head margin weakly concave medially but rounding evenly into the lateral marginsIn profile view, compound eyes ovular and moderately large (OI 23-25), with 13 ommatidia in longest row. Pronotal declivity distinct: dorsal margin of anterior face of pronotum marked by a weak carina; neck and anterior face of pronotum forming a ~120° angle. Mesosoma very weakly sinuate: weakly convex from where it joins the pronotal declivity to the propodeum, the propodeum slightly depressed and concave. Promesonotal suture extending from the posterior margin of the procoxal insertion only 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 against the ground sculpture. Propodeal spiracle moderately well developed, directed posterolaterally, and separated from the propodeal declivity by about five spiracle diameters. Propodeal spines moderately well developed, but short (PSI 24-27), slightly shorter than the propodeal declivity, slightly flared at the base, thin, weakly 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 small, extending from the metacoxal insertion a third of the way to the propodeal spiracle. Petiole moderately long (PLI 158-178), with tubercles anterodorsally. Subpetiolar process in the form of a moderately long, acute, triangular tooth; ventral margin of petiole flat posterior to it. Petiolar peduncle short: comprising about a quarter of the total petiole length. Petiolar node robust, erect, and subquadrate: transition between peduncle and node marked by a rounded angle of ~120°; anterior face forming a ~120° angle with the dorsal face, which is weakly convex, nearly flat; dorsal face meeting the posterior face at a rounded ~90° angle; posterior face forms a ~110° angle with the caudal cylinder. Postpetiole flat anteriorly, bulging slightly anterodorsally before flattening posterodorsally; weakly lobed ventrally.

In dorsal view, humeri moderately well developed: 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 represented by a weak sulcus. Metanotal groove absent: mesonotum and propodeum completely fused and lateral margins converging evenly to the bases of the propodeal spines. Propodeal spines broadly approximated basally and weakly diverging apically, their apices separated from each other by slightly more than their length, the negative space between them "U" shaped. Petiolar peduncle with spiracles weakly protruding past the lateral margins. Petiolar node nearly ovular, but posterior margin flattened; node broader than the peduncle, and evenly grading into the caudal cylinder, which is the same width as the node. Postpetiole narrow (PWI 153-180) and trapezoidal: slightly wider anteriorly than posteriorly. Anterior margin of the postpetiole flat and evenly rounds into the lateral margins, which converge slightly to the rounded posterior corners; posterior margin flat. Metafemur strongly incrassate (FI 357-452).

Sculpture: median clypeal carina present, extending posteriorly to the frontal triangle, and flanked on either side by two equally strong carinae. Lateral clypeal lobes with additional, weaker carinae; ground sculpture shining through weak areolae. Antennal scapes areolate. Cephalic dorsum areolate-rugulose, with rugae over the ground sculpture; concentric costulae surrounding the antennal insertions; costulate sculpture between the frontal carinae. Lateral surfaces of head areolate-rugulose, with fine rugae over the ground sculpture that become stronger between the compound eye and mandibular insertion. Ventral surface of head smooth and shining anteromedially, but otherwise weakly areolate. Pronotal neck weakly areolate. Lateral surfaces mesosoma areolate-rugulose, with fine costulae over the ground sculpture. Propodeal declivity areolate. Dorsal surface of mesosoma predominantly areolate, with fine costulae on the pronotum and fine strigulae on the propodeum. Femora finely, densely areolate. Petiole uniformly areolate; a weak carina present laterally, extending longitudinally from the petiolar spiracle to the caudal cylinder; weak rugulae on the dorsal and posterior faces of the node. Postpetiole uniformly areolate, with weak rugulose sculpture on the lateral faces. First gastral tergite and sternite smooth and shining, without spectral iridescence.

Setae: antennal scapes and funiculi with short, adpressed pilosity. Dorsum of the head, pronotum, waist segments, and gaster with moderately abundant, erect, blunt-tipped setae, the longest of which are about half the width of the compound eye. The head bears ~38, mesosoma ~30, petiole 6, postpetiole ~14, and first gastral tergite ~68 setae. Short, sparse pubescence present over the entire body, but difficult to detect against the densely sculptured integument.

Color: predominantly medium brown, with antennae, mandibles, clypeus, pronotal neck, and legs light brown.

Queen
(n = 1): SL = 0.724; FRS = 0.329; CW = 1.049; CWb = 0.950; PoOC = 0.395; CL = 1.037; EL = 0.341; EW = 0.254; MD = 0.212; WL = 1.882; SPST = 0.373; MPST = 0.495; PEL = 0.539; NOL = 0.245; NOH = 0.262; PEH = 0.438; PPL = 0.348; PW = 1.036; SBPA = 0.511; SPTI = 0.471; PEW = 0.307; PNW = 0.260; PPW = 0.548; HFL = 0.906; HFWmax = 0.254; HFWmin = 0.077; CS = 1.469; ES = 0.468; SI = 76; OI = 32; CI = 92; WLI = 198; SBI = 54; PSI = 20; PWI = 179; PLI = 155; NI = 94; PNWI = 85; NLI = 45; FI = 330.

In full-face view, head subquadrate, slightly longer than broad (CI 92). Mandibles densely striate but shining and armed with five teeth: the apical-most well developed, followed by a less developed preapical tooth and three equally developed smaller teeth. Anterior clypeal margin emarginated medially. Antennal scapes short: when fully retracted, failing to reach the posterior margin of the head capsule by about one and a half times the maximum width of the antennal scape (SI 76). Antennae 12- segmented; antennal club composed of three segments, with the apical-most segment about one and a half times 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 strongly protruding past the lateral margins of the head capsule. Lateral margins of head convex behind the compound eyes; narrower and forming a converging arc between the compound eyes and the mandibular insertions. Posterior margin of head weakly concave medially, rounding evenly into the lateral margins.

In profile view, compound eyes ovular and large (OI 32), with 16 ommatidia in longest row. Mesoscutum rounded evenly anteriorly, covering the dorsal surface of the pronotum, and weakly convex dorsally, nearly flat. Dorsal plane of mesoscutellum even with the level of the mesoscutum. Posterior margin of metanotum extending past the posterior margin of the mesoscutum. Propodeal spiracle well developed, directed posterolaterally, and separated from the propodeal declivity by about four spiracle diameters. Propodeal spines stout and well developed (PSI 20), about as long as the propodeal declivity, tapering evenly from the base, directed posterodorsally, straight, and blunt. Propodeal declivity concave, forming a rounded ~120° angle with the base of the propodeal spines. Propodeal lobes rounded and weakly developed. Metapleural gland moderately large, extending from the metacoxal insertion halfway to the propodeal spiracle. Petiole short (PLI 155), with weakly developed tubercles anterodorsally. Subpetiolar process in the form of a blunt, triangular tooth, which grades evenly into the ventral margin of the petiole posteriorly. Petiolar peduncle short: comprising about a third of the total petiole length. Petiolar node robust and erect: transition between peduncle and node an evenly rounded ~90° angle, with a very slightly concave anterior node face; anterior face forming a rounded ~90° angle with the dorsal face, which is evenly convex; dorsal face rounding evenly into the posterior face; posterior face forms a ~100° angle with the caudal cylinder. Postpetiole evenly rounded anterodorsally, bulging before it transitions into the flattened posterodorsal face; ventral surface weakly lobed.

In dorsal view, mesoscutum covering pronotum anteriorly, but humeri visible laterally as rounded sclerites. Propodeal spines weakly diverging apically, their apices separated from each other by about two and a half times their length. Petiolar peduncle with spiracles not protruding past the lateral margins, but slightly narrowed anterior to them. Petiolar node subovate, slightly broadened transversely. Petiolar node wider than the peduncle, and evenly grading into the caudal cylinder, which is slightly narrower than the node. Postpetiole narrow (PWI 166), anteroposteriorly compressed, and subtrapezoidal: broader anteriorly than posteriorly. Anterior margin of postpetiole flat, with corners marked by rounded angles as it transitions to the lateral margins; lateral margins bulging anteriorly and converging posteriorly; posterior corners angulate; posterior margin flat. Metafemur strongly incrassate (FI 330).

Sculpture: median clypeal carina present, extending from the anterior margin to frontal triangle, and flanked by four weaker carinae. Lateral clypeal lobes with additional weak carinae; ground sculpture smooth and shining medially, but weakly areolate near the margins of the clypeus. Antennal scapes finely areolate-costulate. Cephalic dorsum with areolate ground sculpture that becomes smooth and shining medially, with rugose sculpture that becomes costate between the frontal carinae; fine concentric costulae surround the antennal insertions. Lateral surfaces of head areolate-rugulose, with rugose sculpture overlying the ground sculpture. Ventral surface of head smooth and shining medially, with weak areolate-rugulose sculpture laterally and posteriorly. Pronotal neck areolate-strigulate. Anterior face of pronotum weakly areolate. Lateral face of pronotum rugose. Anepisternum smooth and shining on the posterior half, otherwise anepisternum and katepisternum longitudinally areolate-costulate. Metapleuron and lateral face of propodeum costulate. Propodeal declivity weakly areolate. Mesoscutum with costulae flanking a medial strip of smooth and shining sculpture; lateral margins smooth and shining. Mesoscutellum smooth and shining, with traces of fine costulae laterally. Metanotum smooth and shining. Dorsum of propodeum strigulate. Femora shining, with traces of weak areolate sculpture. Petiole and postpetiole with finely areolate ground sculpture; petiolar node and postpetiole with coarse rugae overlying the ground sculpture. First gastral tergite shining, but with weak, indistinct sculpture. First gastral sternite smooth and shining.

Setae: antennal scapes and funiculi with short, adpressed pilosity. Dorsum of the head, pronotum, waist segments, and gaster with moderately abundant, erect, blunt-tipped setae, the longest of which are about a third of the width 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, with antennae, mandibles, clypeus, pronotal neck, and legs light brown.

Type Material
Holotype worker: MEXICO: Baja California Sur: El Charro, 30 October 1969, E. L. Sleeper, ex dead Agave stalk (LACMENT323199, top specimen on pin).

Paratype workers and gyne: same pin as holotype, 1 worker (middle specimen on pin) 1 dealate gyne (bottom specimen on pin); same data as holotype, 3 workers (LACMENT323198) [LACM] 3 workers (CASENT0758290) [LACM].

Etymology
Geographical, from the Latin ʻbalnearius' (= frequenting baths or bathhouses).