Temnothorax leucacanthus ( Baroni Urbani, 1978 )

Prebus, Matthew M., 2021, Taxonomic revision of the Temnothorax salvini clade (Hymenoptera: Formicidae), with a key to the clades of New World Temnothorax, PeerJ (e 11514) 9, pp. 1-462 : 136-142

Temnothorax leucacanthus ( Baroni Urbani, 1978)

Distribution: Fig. 101D ; worker & gyne: Fig. 105 .

Leptothorax leucacanthus Baroni Urbani, 1978: 460 , figs. 61, 103. Holotype worker & paratype gyne. Guerrero, Mexico.

Temnothorax leucacanthus (Baroni Urbani) : Bolton, 2003: 271. First combination in Temnothorax .

Type material examined: Holotype worker: MEXICO: Guerrero: [locality unknown], [collection date unknown], W.V. Hagen, M.C.Z. Holotype 32434 ( MCZENT00032434 ) [ MCZC] .

Paratype workers and gyne: same data as paratype, 1 worker (MCZENT00577108) [ MCZC] 1 alate gyne (MCZENT577109) [ MCZC] 1 worker (images of CASENT0912957 examined on antweb.org) [ NHMB] .

Non-type material examined: MEXICO: Guerrero: Acapulco , 7 September 1946, F. Bonet, 2 workers (LACMENT323192) [ LACM] .

Geographic range: Low elevations of southern Mexico (Guerrero) ( Fig. 101D ).

Worker diagnosis: The following character combination separates Temnothorax leucacanthus from all other species in the salvini clade: head relatively narrow (CI 80–81); moderately long antennal scapes, which just reach the posterior margin of the head (SI 96–103); mesosoma about one and a half times as long as the width of the head (WLI 143–148); propodeal spines about as long as the length of the propodeal declivity (PSI 38–40); 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 204–224); erect setae on the dorsal surface of the head; integument medium brown.

Similar species: Temnothorax acutispinosus sp. nov., Temnothorax subditivus , T. tenuisculptus , T. tuxtlanus sp. nov., species of the annexus , augusti , fuscatus , and salvini groups. Temnothorax leucacanthus 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: in T. subditivus , the mesosoma is strongly arched, while T. tenuisculptus and T. tuxtlanus sp. nov. have a sinuate profile. Petiolar node shape is also a useful character for separating T. leucacanthus 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. leucacanthus ), and the nodes of the annexus group are erect and subquadrate, as opposed to leaning posteriorly in T. leucacanthus ; T. tenuisculptus , like T. leucacanthus , has a subquadrate petiolar node, but it does not lean posteriorly over the caudal cylinder; T. tuxtlanus sp. nov. and T. acutispinosus sp. nov. have rounded petiolar nodes in profile view. Temnothorax leucacanthus can also be distinguished from T. tuxtlanus sp. nov. and T. acutispinosus sp. nov. 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. leucacanthus 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 T. augusti and T. casanovai sp. nov.), the relatively narrow head (broader in T. leucacanthoides sp. nov.: CI 80–81 vs.> 84); relatively short antennal scapes (SI 96–103 vs.> 105 in T. augusti , T. aureus sp. nov., T. casanovai sp. nov.).

Worker measurements & indices (n = 4): SL = 0.465 –0.508 (0.489); FRS = 0.156 –0.166 (0.161); CW = 0.505 –0.571 (0.541); CWb = 0.453 –0.524 (0.497); PoOC = 0.236 –0.249 (0.244); CL = 0.564 –0.645 (0.614); EL = 0.138 –0.155 (0.145); EW = 0.096 –0.119 (0.106); MD = 0.130 –0.157 (0.147); WL = 0.646 –0.775 (0.720); SPST = 0.248 –0.312 (0.283); MPST = 0.214 –0.248 (0.238); PEL = 0.270 –0.318 (0.295); NOL = 0.146 –0.166 (0.159); NOH = 0.123 –0.146 (0.131); PEH = 0.197 –0.226 (0.213); PPL = 0.140 –0.178 (0.159); PPH = 0.160 –0.183 (0.171); PW = 0.329 –0.376 (0.360); SBPA = 0.126 –0.152 (0.140); SPTI = 0.177 –0.221 (0.201); PEW = 0.108 –0.125 (0.118); PNW = 0.134 –0.153 (0.144); PPW = 0.230 –0.265 (0.252); HFL = 0.471 –0.567 (0.519); HFWmax = 0.153 –0.166 (0.160); HFWmin = 0.041 –0.049 (0.045); CS = 0.735 –0.847 (0.804); ES = 0.186 –0.211 (0.198); SI = 96–103 (99); OI = 23–25 (25); CI = 80–81 (81); WLI = 143–148 (145); SBI = 27–30 (28); PSI = 38–40 (39); PWI = 204–224 (214); PLI = 168–209 (187); NI = 112–131 (122); PNWI = 111–131 (122); NLI = 52–56 (54); FI = 314–405 (357).

Worker description: In full-face view, head subquadrate, longer than broad (CI 80–81). 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 evenly convex medially. Antennal scapes moderately long: when fully retracted, just reaching the posterior margin of the head capsule (SI 96–103). Antennae 12-segmented; antennal club of composed of three segments, with the apical-most segment longer than 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 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 23–25), with 11 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. 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 three spiracle diameters. Propodeal spines well developed and moderately long (PSI 38–40), about as long as the propodeal declivity, tapering evenly from the base, straight, and acute. Propodeal declivity flat, forming a rounded ~100 ° angle with the base of the propodeal spines. Propodeal lobes rounded and weakly developed. Metapleural gland bulla moderately large, extending from the metacoxal insertion two thirds of the way to the propodeal spiracle. Petiole long (PLI 168–209), without tubercles anterodorsally. Subpetiolar process in the form of an acute tooth, ventral margin of petiole weakly bulging posteriorly. Petiolar peduncle long: comprising two thirds of 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 forming a ~100 ° angle with the dorsal face, which is weakly convex; dorsal face rounding evenly into the short posterior face, which forms a ~80 ° angle with the caudal cylinder, overhanging it. Postpetiole evenly rounded anteriorly, flattened dorsally, and weakly lobed ventrally.

In dorsal view, dorsal margin of pronotum delimited from the pronotal declivity by a weak carina. Humeri 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. Metanotal groove absent: mesonotum and propodeum completely fused and lateral margins converging evenly to the bases of the propodeal spines. Propodeal spines narrowly approximated basally, but diverging and becoming parallel apically, their apices separated from each other by less than their length, the negative space between them “U” shaped. Petiolar peduncle with spiracles protruding past the lateral margins; peduncle constricted anterior to them. Petiolar node campaniform: flattened posteriorly; node broader than the peduncle, and about the same width as the caudal cylinder. Postpetiole moderately to very broad (PWI 204–224) and campaniform, articulating with most of the anterior margin of the gaster, leaving small, angulate margins on each side exposed. Anterior margin of the postpetiole convex and evenly rounds into the lateral margins, which weakly diverge to the angulate posterior corners; posterior margin flat. Metafemur strongly incrassate (FI 314–405).

Sculpture: median clypeal carina present, extending posteriorly nearly to the frontal triangle, 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 predominantly areolate, but with costulae overlying the ground sculpture. Lateral surfaces of head sculptured similarly to the dorsum of the head, but with rugulae between the compound eye and the mandibular insertion. Ventral surface of head weakly areolate. Mesosoma with areolate sculpture on the pronotal neck. Lateral surface of the pronotum very weakly areolate-costulate and shining. Lateral face of propodeum, meso- and metapleurae with stronger areolate sculpture; meso- and metapleurae with costulae over the ground sculpture. Propodeal declivity weakly areolate. Dorsal surface of pronotum with rugae over the areolate ground sculpture. Remainder of the mesosoma dorsum predominantly areolate, with weak costulae on the lateral margins. Femora weakly areolate. Petiole and postpetiole shining through weak areolate sculpture on all surfaces. 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, clavate setae, the longest of which are about half the width of the compound eye. The head bears ~22, mesosoma ~22, petiole 2, postpetiole ~10, and first gastral tergite ~38 setae. Short, sparse pubescence present over the entire body, but difficult to detect against the ground sculpture.

Color: predominantly medium brown, with antennae (except for the club), tibiae, tarsi, propodeal spines, and sting light yellow.

Gyne measurements & indices (n = 1): SL = 0.555; FRS = 0.195; CW = 0.682; CWb = 0.646; PoOC = 0.273; CL = 0.720; EL = 0.210; EW = 0.164; MD = 0.152; WL = 1.105; SPST = 0.358; MPST = 0.326; PEL = 0.390; NOL = 0.218; NOH = 0.200; PEH = 0.276; PPL = 0.216; PPH = 0.267; PW = 0.697; SBPA = 0.343; SPTI = 0.305; PEW = 0.186; PNW = 0.233; PPW = 0.409; HFL = 0.648; HFWmax = 0.158; HFWmin = 0.049; CS = 1.006; ES = 0.292; SI = 86; OI = 29; CI = 90; WLI = 171; SBI = 53; PSI = 32; PWI = 220; PLI = 181; NI = 109; PNWI = 125; NLI = 56; FI = 322.

Gyne description: In full-face view, head subquadrate, slightly longer than broad (CI 90). Mandibles densely, finely striate but weakly 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 evenly convex 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 86). Antennae 12-segmented; antennal club composed of three segments, with the apical-most segment longer than 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 very weakly convex, nearly flat, diverging from the mandibular insertions to below the compound eyes. Posterior margin of head weakly convex, rounding evenly into the lateral margins.

In profile view, compound eyes ovular and large (OI 29), with 14 ommatidia in longest row. Mesoscutum rounded evenly anteriorly, not completely covering the dorsal surface of the pronotum, and flat dorsally. Mesoscutellum slightly depressed below the level of the mesoscutum. Posterior margin of metanotum extending slightly past the posterior margin of the mesoscutum. Propodeal spiracle moderately well developed, directed posterolaterally, and separated from the propodeal declivity by about four spiracle diameters. Propodeal spines stout and well developed, moderately long (PSI 32), about as long as the propodeal declivity, tapering evenly from the base, directed posteriorly, straight, and blunt. Propodeal declivity straight and flat, forming a rounded ~100 ° angle with the base of the propodeal spines. Propodeal lobes rounded and very weakly developed. Metapleural gland bulla small, extending from the metacoxal insertion halfway to the propodeal spiracle. Petiole long (PLI 181), without tubercles anterodorsally. Subpetiolar process in the form of a small, very acute tooth, which grades evenly into the ventral margin of the petiole posteriorly; ventral margin of petiole flat. Petiolar peduncle very long: comprising slightly more than half the length of the petiole. Petiolar node robust and erect, nearly squamiform: transition between peduncle and node marked by a rounded angle of ~130 °, resulting in a concave anterior node face; anterior face forming a ~110 ° angle with the dorsal face, which is convex; dorsal face rounding evenly into the short posterior face, which forms a ~85 ° angle with the caudal cylinder, overhanging it. Postpetiole evenly rounded anterodorsally and flattened dorsally; ventral surface weakly lobed.

In dorsal view, mesoscutum leaving a small sliver of the anterior face of the pronotum exposed; humeri visible laterally as weakly angulate sclerites. Propodeal spines weakly diverging apically, their apices separated from each other by about twice their length. Petiolar peduncle with spiracles protruding past the lateral margins, the peduncle narrowed anterior to them. Petiolar node subovate, transversely elongated. Petiolar node wider than the peduncle, about one and a quarter times the width of the caudal cylinder. Postpetiole subquadrate and moderately broad (PWI 220), articulating with most of the anterior margin of the gaster, leaving small, angulate margins on each side exposed. Anterior margin of postpetiole weakly convex, with corners marked by rounded angles as it transitions to the lateral margins, which are parallel to the angulate posterior corners; posterior margin broadly concave. Metafemur strongly incrassate (FI 322).

Sculpture: median clypeal carina present but indistinct, flanked by three equally strong carinae on each side. Lateral clypeal lobes with additional weaker carinae; ground sculpture weakly areolate. Antennal scapes areolate. Cephalic dorsum areolate-rugulose, with rugose-costate sculpture overlying it; fine concentric costulae surrounding the antennal insertions. Lateral surfaces of head sculptured similarly to the dorsal surface, but with costae stronger. Ventral surface of head weakly transversely areolate-costulate. Pronotal neck areolate. Pronotum sculptured similarly to the lateral surface of the head. Lateral face of the propodeum, meso- and metapleurae longitudinally areolate-costulate, becoming weaker on the anterior half of the katepisternum and anterior quarter of the anepisternum. Propodeal declivity transversely areolate-strigulate. Mesoscutum and mesoscutellum with longitudinal striae over areolate ground sculpture. Femora shining through weak areolate sculpture. Petiole and postpetiole areolate, with weaker sculpture on the peduncle and ventral surface of the petiole. First gastral tergite very weakly areolate-costulate on the basal quarter, with faint traces of spectral iridescence. Surface of the first gastral sternite smooth and shining, with weak spectral iridescence.

Setae: antennal scapes and funiculi with short, decumbent pilosity. Dorsum of the head, pronotum, waist segments, and gaster with moderately abundant, erect, clavate 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 ground sculpture.

Color: predominantly medium brown, with antennae (except for the club), tibiae, tarsi, wing bases, propodeal spines, and sting light yellow.

Male: Unknown.

Etymology: Morphological, presumably for the light color of the propodeal spines.

Comments: Temnothorax leucacanthus is known only from a couple of collections in Guerrero state, Mexico. Nothing is known about the biology of this species, but it closely resembles T. leucacanthoides sp. nov. from neighboring Oaxaca state, Mexico, which was collected from the dead stalk of a plant of the family Asteraceae in littoral vegetation.

Figures

Figure 101 Geographical and elevational distribution of the augusti group. (A) Temnothorax augusti (B) T. aureus sp. nov. (C) T. leucacanthoides sp. nov. (D) T. leucacanthus. Colored scale to the left of each map represents elevation in meters. Points in black represent the species named in each subfigure, while points in red represent other members of the species group. Type localities are represented by triangles, non-type localities are represented by circles. Bounding box in inset map shows location of main map. Full-size DOI: 10.7717/peerj.11514/fig-101

Figure 105 Temnothorax leucacanthus. (A–C) Holotype worker (MCZENT00032434). (A) Full-face view. (B) Profile view. (C) Dorsal view. (D–F) Paratype gyne (MCZENT00577109). (D) Full-face view. (E) Profile view. (F) Dorsal view. Scale bars 0.2 mm. Full-size DOI: 10.7717/peerj.11514/fig-105