Temnothorax rugosus

The type series was collected in a trap baited with Vienna sausage, placed in oak trees, about 2-meter height. The habitat was a very steep, south-facing slope of a mountain, covered with oak trees. The specimens were collected within 20 meters distant from one another. (Mackay 2000)

Identification
Prebus (2021) – A member of the rugosus group of the Temnothorax salvini clade. Temnothorax rugosus can be separated from all other species in the salvini clade by the following character combination: anterior clypeal margin emarginate; metanotal groove absent; propodeum not depressed; hind femora weakly to strongly incrassate; petiole cuneiform to subcuneiform; dorsum of head, mesosoma, waist segments and gaster with erect, short, blunt-tipped setae; legs without erect setae; integument testaceous yellow, with legs lighter yellow.

Similar species: Temnothorax acuminatus, Temnothorax nitens, Temnothorax tricarinatus, species of the annexus and silvestrii groups. Temnothorax rugosus may be separated from T. nitens and T. tricarinatus by the moderately incrassate femora (not apparent in smaller workers), and the weakly sculptured first gastral tergite (which is smooth and shining in T. nitens and T. tricarinatus). Many of the preceding characters, in combination, are shared with members of the annexus species group, which T. rugosus is closely related to. Temnothorax rugosus can be separated from the species of the annexus group by the cuneiform petiolar node, which is laterally compressed in dorsal view; all species in the annexus group have quadrate to subquadrate petiolar nodes. Finally, the areolate first gastral tergite is similar to members of the silvestrii group, but members of that group never have incrassate femora, and always have subquadrate petiolar nodes.

The femora of Temnothorax rugosus tend to be incrassate, but the degree of swollenness appears to scale with the size of the worker, with smaller workers having less incrassate femora. Temnothorax rugosus shows some variability in petiolar node shape, eye size, and sculpture among populations (see worker images figures 152 g-i and queen images figure 152 j-l below in the caste section). In the petiolar node, there appears to be a complete range of variation between completely cuneiform, with no differentiation between the dorsal and posterior declivitous face, to subcuneiform, with a very short but distinct posterior face and a deeply sloping dorsal face.

Mackay (2000) - This is a medium sized, light brown species with a 12-segmented antenna, in which the head and mesosoma are coarsely rugose. It is one of the few species in the subgenus which has a very lightly sculptured gaster, which is not always obvious. The hind femur is somewhat incrassate. The petiole is narrow as seen from above, with a laterally "pinched" node, the postpetiole has fine, longitudinal striae. This species may be related to Temnothorax silvestrii, with similar sculpturing on the gaster (note: the sculpturing is very fine and difficult to see in some specimens), and a thickened hind femur, but is easily distinguished as the apex of the petiolar node is rather sharp, not broad and blunt as in Temnothorax silvestrii. The top of the mesosoma of both species is rugose. The shape of the petiole (forming an acute peak where anterior face meets top of node) easily separates it. It is quite different from all of the other species with sculptured gasters. It is very distinct from Temnothorax maryanae (=Temnothorax nevadensis), and can be easily distinguished as the side of the pronotum is rugose, whereas the side of the pronotum of Temnothorax maryanae is punctate.

The sculpture on the gaster of the holotype is very obvious, that on the 2 paratypes is less obvious. The latter specimens could key to Temnothorax tricarinatus. Temnothorax rugosus differs in that the sculpture is much coarser, with the rugae on the head and dorsum of the mesosoma very well developed. The petiole is much narrower as seen from above, and pinched. The sculpture of the postpetiole is more coarsely sculptured, with costulae at least on the sides. The clypeus has several poorly developed carinae, not the 3 well developed carinae as in Temnothorax tricarinatus. Temnothorax rugosus could also be confused with Temnothorax texanus, but can be separated as the rugae on the dorsum of the postpetiole of Temnothorax texanus are transverse, whereas the rugae in the same position of Temnothorax rugosus are longitudinal.

Distribution
Mexico: Mid-to-high elevations of southwestern Texas to Hidalgo State, Mexico.

Distribution based on Regional Taxon Lists
Nearctic Region: United States. Neotropical Region: Mexico.

Habitat
Nests in oak (Quercus) trees, this species has been found in oak and oak-pine forest.

Biology
Prebus (2021) - After inspecting the collections of the LACM, I found that W.S. Creighton collected Temnothorax rugosus in a number of localities spanning northern Mexico and southwestern Texas, in addition to the type locality near Monterrey. Like members of the annexus group, which it is closely affiliated with, T. rugosus nests arboreally in the branches a number of different Quercus spp. (including Q. canbyi, Q. clivicola, Q. grisea, and Q. polymorpha), as well as Cercis reniformis and Rhus spp. at mid elevations. Temnothorax rugosus is also recorded as being collected from Tillandsia carlos-hankii in oak-pine forest near Ixtepeji, Oaxaca (Franco Méndez, 2008).

Nomenclature

 *  rugosus. Leptothorax (Myrafant) rugosus Mackay, W.P., 2000: 399, figs. 18, 160 (w.) MEXICO. Combination in Temnothorax: Bolton, 2003: 272.

Worker
Mandibles with 5 well defined teeth; anterior border of clypeus convex, clypeus with well developed medial carina and several lateral carinae; vertex concave; mesosoma with none of the sutures breaking surface, although area of mesopropodeal suture depressed; propodeal angles well developed, acute, nearly formed into spines, about half as long as distance between bases; petiole with dull spine on peduncle, directed anteriorly, anterior and posterior faces nearly straight, meeting at a distinct angle, petiolar node thus acute in profile; femora of all legs, especially posterior leg, thickened. Erect hairs scattered over surface, coarse and blunt, maximum length 0.05mm, absent from antennae and legs, which have decumbent hairs. Sculpture very rough, consisting of rugae on all surfaces except gaster, intrarugal spaces heavily punctate, gaster with very fine punctation, nearly smooth and shining.

Color: light brownish-yellow, gaster and top of head slightly darker.

Worker measurement (mm): HL 0.67-0.70, HVV 0.58-0.59, SL 0.49-0.50, EL 0.16-0.17, WL 0.82-0.83, PW 0.14-0.15, PL 0.19-0.23, PPW 0.27-0.28, PPL 0.18-0.19. Indices: CI 84-87, SI 71-73, PI 65-74, PPI 147-150.

Prebus (2021) - (n = 27): SL = 0.465-0.602 (0.527); FRS = 0.207-0.279 (0.228); CW = 0.610-0.800 (0.700); CWb = 0.563-0.733 (0.642); PoOC = 0.265-0.325 (0.288); CL = 0.701-0.874 (0.773); EL = 0.157-0.255 (0.198); EW = 0.116-0.166 (0.142); MD = 0.173-0.217 (0.197); WL = 0.824-1.095 (0.948); SPST = 0.141-0.219 (0.182); MPST = 0.203-0.334 (0.281); PEL = 0.242-0.362 (0.291); NOL = 0.147-0.230 (0.178); NOH = 0.105-0.180 (0.133); PEH = 0.226-0.303 (0.260); PPL = 0.170-0.289 (0.211); PPH = 0.210-0.306 (0.244); PW = 0.368-0.502 (0.428); SBPA = 0.135-0.213 (0.160); SPTI = 0.148-0.241 (0.187); PEW = 0.149-0.217 (0.178); PNW = 0.066-0.117 (0.090); PPW = 0.245-0.393 (0.290); HFL = 0.484-0.680 (0.578); HFWmax = 0.148-0.209 (0.177); HFWmin = 0.049-0.081 (0.059); CS = 0.914-1.170 (1.029); ES = 0.219-0.327 (0.269); SI = 77-89 (82); OI = 24-29 (26); CI = 80-87 (83); WLI = 139-157 (148); SBI = 22-29 (25); PSI = 17-22 (19); PWI = 140-181 (163); PLI = 113-176 (139); NI = 105-173 (135); PNWI = 38-67 (50); NLI = 49-75 (61); FI = 225-354 (301).

In full-face view, head subquadrate, longer than broad (CI 80-87). 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 two times the maximum width of the antennal scape (SI 77-89). 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 two times the maximum width of the antennal scape. Compound eyes moderately protruding past the lateral margins of the head capsule. margin of head weakly convex, forming a continuous arc from the mandibular insertions to the posterior margin of the head. Posterior head margin concave medially, rounding evenly into the lateral margins.

In profile view, compound eyes ovular and moderately large (OI 24-29), with 13 ommatidia in longest row. Pronotal declivity distinct: dorsal margin of anterior face of pronotum marked by a weak carina and change in sculpture; neck and anterior face of pronotum forming a ~120° angle. Mesosoma very weakly sinuate: promesonotum forming an even convexity from where it joins the pronotal declivity; propodeum weakly depressed below the level of the promesonotum and descending sharply to the base of the propodeal spines on the posterior quarter. Promesonotal suture extending from the posterior margin of the procoxal insertion to the mesothoracic spiracle, which is 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 four spiracle diameters. Propodeal spines weakly developed and short (PSI 17-22), about a third as long as the propodeal declivity, flared at the base, stout, triangular, and acute. Propodeal declivity straight, forming a rounded ~120° 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 113-176), with tubercles anterodorsally. Subpetiolar process in the form of a blunt, triangular tooth which grades evenly into the ventral petiole margin posteriorly. Petiolar peduncle short: comprising about a quarter of the total petiole length. Petiolar node truncate but dorsum is extremely angled, so that in many specimens it appears cuneiform: anterior face forming a sharp ~90° angle with the dorsal face, which is flat; dorsal face meeting the posterior face at a sharp ~120° angle; very short posterior face forms a ~110° angle with the caudal cylinder. Postpetiole evenly convex anterodorsally; weakly lobed ventrally.

In dorsal view, humeri developed: angulate anterolaterally and slightly wider than the rest of the mesosoma; mesothoracic spiracles 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 and disruption in the ground sculpture. 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 diverging apically, their apices separated from each other by about twice their length, the negative space between them "U" shaped. Petiolar peduncle with spiracles weakly protruding past the lateral margins. Petiolar node, when viewed at posterodorsal angle, cuneiform: narrowed apically and flat dorsally; node narrower than the peduncle and the caudal cylinder. Postpetiole narrow (PWI ~ 163) and campaniform. Anterior margin of the postpetiole convex and rounds evenly into the lateral margins; lateral margins parallel to each other; posterior corners rounded; posterior margin flat. Metafemur moderately to strongly incrassate (FI 225-354).

Sculpture: median clypeal carina present, extending posteriorly to the frontal triangle, and flanked on either side by three weaker carinae. Lateral clypeal lobes with additional, weaker carinae; ground sculpture shining through weak areolae. Antennal scapes areolate. Cephalic dorsum areolate, with costa over the ground sculpture, which become rugose on the posterior sixth of the head; concentric rugulae surrounding the antennal insertions. Lateral surfaces of head areolate, with coarse rugae over the ground sculpture. Ventral surface of head smooth and shining medially, but otherwise weakly areolate with weak costulae. Pronotal neck areolate. Lateral surfaces of mesosoma weakly areolate, with coarse, costae over the ground sculpture; region between the propodeal spiracle and propodeal spines areolate, without rugae. Propodeal declivity areolate, with fine strigulae. Dorsal surface of mesosoma weakly areolate, with coarse costae that are rugose on the pronotum and the propodeum. Femora finely, weakly areolate. Petiole uniformly areolate; a weak carina present laterally, extending longitudinally from the petiolar spiracle to the caudal cylinder; rugae on lateral faces of the node. Postpetiole uniformly areolate, with rugose sculpture on the dorsal and lateral surfaces. First gastral tergite shining through weak areolate sculpture; without spectral iridescence. First gastral sternite smooth and shining, without spectral iridescence.

Setae: antennal scapes and funiculi with short, subdecumbent 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 ~50, mesosoma ~26, petiole 8, postpetiole ~32, and first gastral tergite ~72 setae. Short, sparse pubescence present over the entire body, but difficult to detect against the densely sculptured integument.

Color: predominantly testaceous yellow, with legs lighter yellow.

Queen
Prebus (2021) - (n = 5): SL = 0.518-0.600 (0.556); FRS = 0.264-0.309 (0.291); CW = 0.783-0.831 (0.802); CWb = 0.726-0.782 (0.746); PoOC = 0.304-0.319 (0.312); CL = 0.824-0.880 (0.851); EL = 0.233-0.277 (0.253); EW = 0.171-0.207 (0.191); MD = 0.169-0.196 (0.183); WL = 1.324-1.477 (1.401); SPST = 0.202-0.233 (0.223); MPST = 0.322-0.383 (0.354); PEL = 0.312-0.382 (0.355); NOL = 0.204-0.228 (0.213); NOH = 0.145-0.168 (0.155); PEH = 0.300-0.351 (0.319); PPL = 0.215-0.238 (0.224); PPH = 0.314-0.376 (0.345); PW = 0.783-0.838 (0.802); SBPA = 0.300-0.391 (0.338); SPTI = 0.268-0.340 (0.310); PEW = 0.222-0.269 (0.237); PNW = 0.120-0.185 (0.146); PPW = 0.378-0.465 (0.413); HFL = 0.644-0.718 (0.667); HFWmax = 0.166-0.189 (0.178); HFWmin = 0.053-0.069 (0.062); CS = 1.138-1.216 (1.171); ES = 0.319-0.381 (0.349); SI = 71-77 (75); OI = 28-33 (30); CI = 85-90 (88); WLI = 182-200 (188); SBI = 41-52 (45); PSI = 15-17 (16); PWI = 165-186 (174); PLI = 145-176 (158); NI = 121-146 (138); PNWI = 52-79 (62); NLI = 53-67 (60); FI = 242-313 (289).

In full-face view, head subquadrate, longer than broad (CI 85-90). 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 two times the maximum width of the scape (SI 71-77). 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, but parallel to each other between the compound eyes and the mandibular insertions. Posterior head margin weakly concave medially, rounding evenly into the lateral margins.

In profile view, compound eyes ovular and large (OI 28-33), with 17 ommatidia in longest row. Mesoscutum rounded evenly anteriorly, covering the dorsal surface of the pronotum, and flat dorsally. Mesoscutellum on the same plane as the mesoscutum and flat dorsally. Posterior margin of metanotum extending slightly 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, weakly developed, and short (PSI 15-17), about a third as long as the propodeal declivity, flared at the base, triangular, and blunt. Propodeal declivity straight and flat, forming a rounded ~120° angle with the base of the propodeal spines. Propodeal lobes rounded. Metapleural gland bulla small, extending from the metacoxal insertion halfway to the propodeal spiracle. Petiole moderately long (PLI 145-176), with 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 quarter of the total petiole length. Petiolar node truncate but dorsum is extremely angled, so that in many specimens it appears cuneiform: anterior face forming a sharp ~90° angle with the dorsal face, which is flat; dorsal face meeting the posterior face at a sharp ~120° angle; very short posterior face forms a ~110° angle with the caudal cylinder. Postpetiole evenly convex anterodorsally, flat posterodorsally; weakly lobed ventrally.

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 three times their length. Petiolar peduncle with spiracles weakly protruding past the lateral margins. Petiolar node, when viewed posterodorsally, tapering apically so the apex is about half the width of the base; dorsal margin emarginate medially. Postpetiole narrow (PWI 165-186), anteroposteriorly compressed, and subquadrate. Anterior margin of postpetiole weakly convex but emarginated medially; anterior corners marked by rounded ~100° angles as it transitions to the lateral margins; lateral margins parallel to each other; posterior corners rounded; posterior margin weakly concave. Metafemur weakly to strongly incrassate (FI 242-313).

Sculpture: median clypeal carina present, extending from the anterior margin nearly to frontal triangle, and flanked on either side by three equally strong carinae. Lateral clypeal lobes with additional weaker carinae; ground sculpture weakly areolate. Antennal scapes finely areolate. Cephalic dorsum areolate, with costae over the ground sculpture, which become rugose on the posterior sixth of the head; concentric rugulae surrounding the antennal insertions. Lateral surfaces of head areolate, with coarse rugae over the ground sculpture. Ventral surface of head smooth and shining medially, but otherwise weakly areolate with weak costulae. Pronotal neck areolate. Anterior face of pronotum weakly areolate. Lateral surfaces of the mesosoma sculptured similarly to the dorsum of the head. Propodeal declivity areolate-strigulate. Mesoscutum and mesoscutellum with fine costulae over finely areolate ground sculpture. Metanotum finely areolate. Propodeum areolate, with coarse costae. Femora shining through weak areolate sculpture. Petiole uniformly areolate; a weak carina present laterally, extending longitudinally from the petiolar spiracle to the caudal cylinder; coarse rugae on lateral faces of the node. Postpetiole uniformly areolate, with weak rugose sculpture on the dorsal and lateral faces. First gastral tergite shining through weak areolate sculpture; without spectral iridescence. First gastral sternite smooth and shining.

Setae: antennal scapes and funiculi with short, subdecumbent 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 testaceous yellow, with legs lighter yellow. Wing bases dark brown.

Type Material
MEXICO, Nuevo Leon; EI Salto (Zaragosa), 10-vi-1988, 1415 meters, W. Mackay #11012-8 and #11012-10. Holotype worker, and two paratype workers.

Etymology
Morphological. "Name based on the rugose head and mesosoma."

References based on Global Ant Biodiversity Informatics

 * Dattilo W. et al. 2019. MEXICO ANTS: incidence and abundance along the Nearctic-Neotropical interface. Ecology https://doi.org/10.1002/ecy.2944
 * Vásquez-Bolaños M. 2011. Lista de especies de hormigas (Hymenoptera: Formicidae) para México. Dugesiana 18: 95-133