Temnothorax leucacanthoides

Identification
Prebus (2021) - The following character combination separates Temnothorax leucacanthoides from all other species in the salvini clade: head relatively broad (CI 84-89); moderately long antennal scapes, which just reach the posterior margin of the head (SI 86-96); mesosoma about one and a half times as long as the width of the head (WLI 136-143); propodeal spines about as long as the length of the propodeal declivity (PSI 39-42); petiolar node subquadrate, overhanging the caudal cylinder of the petiole; postpetiole moderately to very broad, more than two times the width of the petiole in dorsal view (PWI 202-224); integument medium brown; erect setae on the dorsal surface of the head.

Similar species: Temnothorax acutispinosus, Temnothorax subditivus, Temnothorax tenuisculptus, Temnothorax tuxtlanus, species of the annexus, augusti, fuscatus, and salvini groups. Temnothorax leucacanthoides can be distinguished from the first three species by the shape of the dorsal margin of the mesosoma in profile, which is weakly, evenly convex (with the metanotal groove slightly impressed in some specimens): in T. subditivus, the mesosoma is strongly arched, while T. tenuisculptus and T. tuxtlanus have a sinuate profile. Petiolar node shape is also a useful character for separating T. leucacanthoides from the above taxa: T. subditivus and the potentially co-occurring members of the salvini group have a squamiform petiolar node, which is much broader than the peduncle in dorsal view (only slightly wider in T. leucacanthoides), and the nodes of the annexus group are erect and subquadrate, as opposed to leaning posteriorly in T. leucacanthoides; T. tenuisculptus, like T. leucacanthoides, has a subquadrate petiolar node, but it does not lean posteriorly over the caudal cylinder; T. tuxtlanus and T. acutispinosus have rounded petiolar nodes in profile view. Temnothorax leucacanthoides can also be distinguished from T. tuxtlanus and T. acutispinosus by the presence of erect setae on the dorsum of the propodeum. The potentially co-occurring members of the fuscatus group have a low, elongate petiolar node in profile view. Finally, T. leucacanthoides can be separated from fellow members of the augusti group by the combination of long propodeal spines, which are about as long as the length of the propodeal declivity (shorter than the declivity in Temnothorax augusti and Temnothorax casanovai), the relatively broad head (narrower in all other augusti group species: CI >84 vs. < 82); relatively short antennal scapes (SI 86-96 vs. >105 in T. augusti, Temnothorax aureus, T. casanovai).

Distribution based on Regional Taxon Lists
Neotropical Region: Mexico.

Nomenclature

 * . Temnothorax leucacanthoides Prebus, 2021: 132, figs. 101C, 104 (w.) MEXICO (Oaxaca).

Worker
(n = 7): SL = 0.521-0.573 (0.547); FRS = 0.182-0.197 (0.189); CW = 0.618-0.658 (0.64); CWb = 0.578-0.611 (0.596); PoOC = 0.251-0.263 (0.256); CL = 0.680-0.704 (0.693); EL = 0.158-0.166 (0.162); EW = 0.112-0.126 (0.120); MD = 0.171-0.188 (0.179); WL = 0.815-0.863 (0.836); SPST = 0.319-0.360 (0.335); MPST = 0.249-0.276 (0.261); PEL = 0.349-0.376 (0.363); NOL = 0.181-0.206 (0.192); NOH = 0.122-0.150 (0.137); PEH = 0.240-0.260 (0.251); PPL = 0.154-0.187 (0.170); PPH = 0.198-0.225 (0.211); PW = 0.420-0.454 (0.437); SBPA = 0.159-0.184 (0.171); SPTI = 0.259-0.280 (0.267); PEW = 0.150-0.165 (0.156); PNW = 0.174-0.192 (0.184); PPW = 0.317-0.342 (0.330); HFL = 0.555-0.603 (0.583); HFWmax = 0.145-0.173 (0.162); HFWmin = 0.044-0.054 (0.048); CS = 0.920-0.957 (0.942); ES = 0.214-0.229 (0.221); SI = 86-96 (92); OI = 23-24 (24); CI = 84-89 (86); WLI = 136-143 (140); SBI = 28-30 (29); PSI = 39-42 (40); PWI = 202-224 (211); PLI = 198-244 (215); NI = 127-155 (141); PNWI = 112-123 (118); NLI = 50-55 (53); FI = 302-393 (341).

In full-face view, head subquadrate, longer than broad (CI 84-89). 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 moderately long: when fully retracted, just reaching the posterior margin of the head capsule (SI 86-96). Antennae 12-segmented; antennal club of composed of three segments, with the apical-most segment slightly longer than the preceding two in combination. Frontal carinae long, extending past the antennal toruli by about three 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 medially weakly emarginate, but predominantly flat, rounding evenly into the lateral margins.

In profile view, compound eyes ovular and moderately large (OI 23-24), with 10 ommatidia in longest row. Pronotal declivity distinct, neck and anterior face of pronotum forming a ~120° angle; anterior face and dorsal face meeting at a ~120° angle. Mesosoma evenly convex from where it joins the pronotal declivity to the propodeal spines, but the metanotal groove slightly impressed in some specimens. Promesonotal suture extending from the posterior margin of the procoxal insertion only to the mesothoracic spiracle, which is moderately well developed. Propodeal spiracle moderately well developed, directed posterolaterally, and separated from the propodeal declivity by about three and a half spiracle diameters. Propodeal spines well developed, and moderately long (PSI 39-42), about as long as the propodeal declivity, tapering evenly from the base, upturned at the tips, and acute. Propodeal declivity flat, 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 halfway to the propodeal spiracle. Petiole long (PLI 198-244), without tubercles anterodorsally. Subpetiolar process in the form of an acute tooth, ventral margin of petiole very weakly bulging medially. Petiolar peduncle moderately long: half the length of the petiole. Petiolar node robust and erect, nearly squamiform: transition between peduncle and node marked by a rounded angle of ~120°, resulting in a concave anterior node face; anterior face rounding evenly into the dorsal face, which is evenly convex; dorsal face rounding evenly into the posterior face, which forms a ~80° angle with the caudal cylinder, overhanging it. Postpetiole flat anteriorly, rounding evenly into the flattened dorsal face; weakly lobed ventrally.

In dorsal view, dorsal margin of pronotum delimited from the pronotal declivity by a carina. Humeri developed: evenly rounded and wider than the rest of the mesosoma; mesothoracic spiracles very weakly protruding past the lateral margins of the mesosoma, visible as slight angles where the pronotum meets the mesonotum. Metanotal groove visible in some specimens as a slight disruption in the sculpture. Propodeal spines narrowly approximated basally, but diverging rapidly and becoming parallel apically, their apices separated from each other by slightly less than their length, the negative space between them V shaped. Petiolar peduncle with spiracles protruding past the lateral margins; peduncle constricted anterior to them. Petiolar node campaniform: very weakly convex posteriorly, nearly flat; node broader than the peduncle, and slightly wider than the caudal cylinder. Postpetiole subquadrate and moderately to strongly broad (PWI 202-224), articulating with most of the anterior margin of the gaster, leaving small, angulate margins on each side exposed. Anterior margin of the postpetiole very weakly convex, nearly flat, and evenly rounding into the lateral margins, which weakly diverge to the angulate posterior corners; posterior margin broadly concave. Metafemur strongly incrassate (FI 302-393).

Sculpture: median clypeal carina present, extending posteriorly to the level of the antennal toruli, and flanked on either side by two equally strong carinae. Lateral clypeal lobes with additional, weaker carinae; ground sculpture weakly areolate. Antennal scapes areolate. Cephalic dorsum areolate, but with rugae overlying the ground sculpture, becoming costate between the frontal carinae; concentric costulae surrounding the antennal insertions. Lateral surfaces of head sculptured similarly to the dorsum of the head, but with rugae becoming weaker posterior to the compound eye. Ventral surface of head predominantly smooth and shining. Mesosoma with areolate sculpture on the pronotal neck. Lateral surface of the mesosoma strongly areolate, with overlying rugose-costate sculpture on the pronotum, on the border of the meso- and metapleurae, and on the propodeal declivity. Dorsal surface of mesosoma areolate-rugulose, with rugae overlying the ground sculpture. Femora shining through weakly areolate sculpture. Petiole and postpetiole predominantly areolate, but sculpture is weaker on the petiolar peduncle, dorsal face of the petiolar node, and the anteromedial part of the postpetiole. First gastral tergite smooth and shining, with weak spectral iridescence. First gastral sternite smooth and shining, without spectral iridescence.

Setae: antennal scapes and funiculi with short, decumbent pilosity. Dorsum of the head, pronotum, waist segments, and gaster with moderately abundant, erect, blunt-tipped setae, the longest of which are about the width of the compound eye. The head bears ~32, mesosoma ~38, petiole 10, postpetiole ~20, and first gastral tergite ~72 setae. Short, sparse pubescence present over the entire body, but difficult to detect against the ground sculpture.

Color: predominantly medium brown, with mandibles, antennae, pronotal neck, tibiae, tarsi, propodeal spines, and sting testaceous yellow.

Type Material
Holotype worker: MEXICO: Oaxaca: Cerro Largo, 6 km W Puerto Angel, 20 m, 15.666667° N 96.550000° W, 22 March 2006, P.S. Ward #15573, littoral vegetation, ex dead stalk of Asteraceae (CASENT0756102, top specimen on pin).

Paratype workers: same pin as holotype, 1 worker (CASENT0756102, bottom specimen on pin) [CASC]; same data as holotype, 1 worker (CASENT0732606) 1 worker (CASENT0758708) [UCDC] 3 workers (CASENT0916001).

Etymology
Morphological, for the close resemblance to Temnothorax leucacanthus.