Temnothorax terrigena ( Wheeler, 1903b )

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 : 447-453

Temnothorax terrigena ( Wheeler, 1903b)

Distribution, worker & gyne: Fig. 170 .

Leptothorax terrigena Wheeler, 1903b: 254 . Syntype workers and dealate gyne: McNeil, Texas, U.S.A. One syntype worker here designated lectotype.

Leptothorax (Myrafant) terrigena (Wheeler) : Smith, 1979: 1395. First combination in Leptothorax (Myrafant) .

Temnothorax terrigena (Wheeler) : Bolton, 2003: 271. First combination in Temnothorax .

Type material examined: Lectotype worker of Leptothorax terrigena : U.S.A.: Texas: Travis County, McNeil , 22 February 1902, co-type A.M. N.H., bottom specimen on pin (M.C.Z. Type 21038, MCZENT00522078) [ MCZC].

Paralectotype workers and gyne of Leptothorax terrigena : same pin as lectotype, 1 dealate gyne, 1 worker (top and middle specimens on pin) [ MCZC]; same data as lectotype, 4 workers (M.C.Z. Type 21038, MCZENT00031038) [ MCZC] 3 workers (LACMENT181910) [ LACM] 3 workers (M.C.Z. Type 21038, USNMENT00528965) [ USNM] 3 workers (CASENT0105624) [ USNM] .

Non-type material examined: MEXICO: Tamaulipas: Victoria, [intercepted in quarantine], 7 November 1947, [no collector data], Lar-45405, 47-16324, on Cycad plant, 1 dealate gyne & 7 workers (CASENT0758302-CASENT0758305) [ USNM] .

U.S.A.: Texas: Cameron County: Laguna Atacosa National Wildlife Refuge, 5 m, 15 December 1984, P.S. Ward #7197-3, coastal mesquite scrub, ground foragers, 1 worker (CASENT0104775) [ UCDC]; Travis County : Austin, [no collection date], W.M. Wheeler, 2 workers (CASENT0758301) [ USNM] .

Geographic range: Low elevations, Texas, U.S.A. to Tamaulipas, Mexico ( Fig. 170G ).

Worker diagnosis: Temnothorax terrigena can be separated from all other species in the salvini clade by the following character combination: in profile view, dorsum of mesosoma weakly convex; metanotal groove not impressed; propodeum not depressed below the level of the promesonotum; propodeal spines shorter than the propodeal declivity and directed posterodorsally; hind femora weakly to moderately incrassate; petiolar node subquadrate, not leaning posteriorly, and rounded dorsally; petiolar node as long as, or only slightly longer than high; posterior face of petiolar node about the same height as the anterior face; postpetiole moderately broad, greater than 1.5 times the width of the caudal cylinder of the petiole, but less than 2.2 times; setae on head, mesosoma, waist segments and gaster erect, short, sparse and blunt (never long and tapering); integument predominantly yellow.

Similar species: Temnothorax andrei , T. carinatus , T. goniops , T. pilicornis sp. nov., T. rugosus , T. subditivus (light form), T. torrei . Temnothorax terrigena differs from T. pilicornis sp. nov. by the pilosity on the antennal scapes and the shape of the petiolar node: the scape setae are subdecumbent and the posterior face of the petiolar node is much shorter than the anterior face in T. pilicornis sp. nov. The pedunculate petiole with an erect subquadrate node will separate T. terrigena from T. subditivus , which has a squamiform petiolar node. Temnothorax rugosus has a cuneiform to subcuneiform petiolar node, as opposed to the erect and compact petiolar node of T. terrigena . Temnothorax terrigena differs from T. torrei by the presence of four erect setae on the dorsum of the petiolar node, as opposed to two. Temnothorax terrigena can be distinguished from T. goniops by the relatively short propodeal spines, which are shorter than the propodeal declivity (longer than the declivity in T. goniops ). Temnothorax andrei has a relatively narrow postpetiole, and both T. andrei and T. carinatus differ from T. terrigena by their head sculpture, which typically has a medial strip of smooth and shining sculpture, as opposed to the uniformly areolate head of T. terrigena .

Worker measurements & indices (n = 14): SL = 0.349 –0.403 (0.378); FRS = 0.133 –0.165 (0.152); CW = 0.425 –0.482 (0.456); CWb = 0.395 –0.457 (0.423); PoOC = 0.208 –0.233 (0.219); CL = 0.511 –0.561 (0.536); EL = 0.102 –0.131 (0.117); EW = 0.080 –0.101 (0.089); MD = 0.104 –0.123 (0.112); WL = 0.539 –0.634 (0.586); SPST = 0.128 –0.163 (0.143); MPST = 0.177 –0.222 (0.194); PEL = 0.211 –0.265 (0.228); NOL = 0.101 –0.134 (0.118); NOH = 0.080 –0.110 (0.100); PEH = 0.159 –0.224 (0.198); PPL = 0.140 –0.180 (0.156); PW = 0.274 –0.314 (0.298); SBPA = 0.127 –0.154 (0.141); SPTI = 0.140 –0.180 (0.165); PEW = 0.113 –0.146 (0.130); PNW = 0.134 –0.171 (0.154); PPW = 0.237 –0.284 (0.256); HFL = 0.311 –0.405 (0.362); HFWmax = 0.102 –0.129 (0.116); HFWmin = 0.038 –0.050 (0.044); CS = 0.651 –0.738 (0.691); ES = 0.142 –0.178 (0.161); SI = 83–93 (89); OI = 21–26 (23); CI = 76–82 (79); WLI = 135–143 (138); SBI = 30–36 (33); PSI = 21–28 (24); PWI = 180–215 (198); PLI = 123–161 (147); NI = 98–148 (118); PNWI = 106–134 (119); NLI = 43–61 (52); FI = 225–300 (268).

Worker description: In full-face view, head subquadrate and elongate (CI 76–82). Mandibles densely 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 strongly convex 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 83–93). Antennae 12-segmented; antennal club of composed of three segments, with the apical-most segment about twice 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 very weakly convex, nearly flat, forming a continuous arc from the mandibular insertions to the posterior margin of the head. Posterior head margin concave medially but rounding evenly into the lateral margins.

In profile view, compound eyes ovular and moderately large (OI 21–26), with 8 ommatidia in longest row. Pronotal declivity distinct: neck and anterior face of pronotum forming a ~110 ° angle; anterior face and dorsum of mesosoma forming a ~120 ° angle. Mesosoma very weakly convex from where it joins the pronotal neck 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 weakly developed, directed posterolaterally, and separated from the propodeal declivity by about four spiracle diameters. Propodeal spines weakly developed and short (PSI 21–28), about half as long as the propodeal declivity, flared at the base, triangular, and acute. Propodeal declivity flat, forming a rounded ~120 ° 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 short (PLI 123–161), without tubercles anterodorsally. Subpetiolar process in the form of a moderately large, blunt, triangular tooth which grades evenly into the ventral margin of the petiole posteriorly; ventral margin of petiole flat posterior to it. Petiolar peduncle short: comprising about a third of the total petiole length. Petiolar node robust, erect, and rounded-subquadrate: transition between peduncle and node marked by a rounded angle of ~120 °; anterior face forming a ~100 ° angle with the dorsal face, which is convex; dorsal face meeting the posterior face at a rounded ~90 ° angle; posterior face forms a ~90 ° angle with the caudal cylinder. Postpetiole strongly convex anteriorly, weakly convex dorsally, and weakly lobed ventrally.

In dorsal view, humeri developed and distinct: 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 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, but not noticeably constricted anterior to them. Petiolar node campaniform and antero-posteriorly compressed: convex anteriorly and flat posteriorly; node slightly wider than the peduncle and caudal cylinder. Postpetiole moderately broad (PWI 180–215) and subtrapezoidal, articulating with the nearly the entire anterior margin of the gaster, but leaving small angles on either side exposed. Anterior margin of the postpetiole weakly convex and evenly rounds into the lateral margins; lateral margins converge slightly to the rounded posterior corners; posterior margin broadly concave. Metafemur weakly to moderately incrassate (FI 225–300).

Sculpture: median clypeal carina present but weak, 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 weakly areolate. Cephalic dorsum and lateral surfaces of head uniformly areolate. Ventral surface of head shining through weak areolae. Pronotal neck and anterior face of the pronotum areolate. Lateral surfaces of mesosoma and shining through weak areolate sculpture. Propodeal declivity areolate. Dorsal surface of mesosoma uniformly areolate. Femora shining, with traces of weak areolate sculpture. Petiole and postpetiole areolate, with anterior and dorsal surfaces of petiolar node, and dorso-medial surface of postpetiole smooth and shining. 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 sparse, erect, blunt-tipped, nearly clavate setae, the longest of which are about the half the width of the compound eye. The head bears ~28, mesosoma ~16, petiole 6, postpetiole ~10, and first gastral tergite ~36 setae. Short, sparse pubescence present over the entire body, but difficult to detect against the lightly colored integument.

Color: predominantly yellow, with masticatory margin of mandibles dark brown; antennal club testaceous yellow.

Gyne measurements & indices (n = 2): SL = 0.437; FRS = 0.190 –0.202 (0.196); CW = 0.596 –0.605 (0.601); CWb = 0.541 –0.554 (0.548); PoOC = 0.214 –0.221 (0.218); CL = 0.599 –0.613 (0.606); EL = 0.189 –0.209 (0.199); EW = 0.154; MD = 0.108 –0.112 (0.110); WL = 0.969 –0.989 (0.979); SPST = 0.191 –0.207 (0.199); MPST = 0.249 –0.266 (0.258); PEL = 0.310 –0.319 (0.315); NOL = 0.152 –0.165 (0.159); NOH = 0.115 –0.133 (0.124); PEH = 0.247 –0.268 (0.258); PPL = 0.163 –0.211 (0.187); PW = 0.575 –0.601 (0.588); SBPA = 0.288 –0.306 (0.297); SPTI = 0.257 –0.268 (0.263); PEW = 0.161 –0.202 (0.182); PNW = 0.216 –0.217 (0.217); PPW = 0.339 –0.346 (0.343); HFL = 0.466 –0.482 (0.474); HFWmax = 0.099 –0.124 (0.112); HFWmin = 0.043 –0.044 (0.044); CS = 0.841 –0.861 (0.851); ES = 0.266 –0.286 (0.276); SI = 79–81 (80); OI = 32–33 (32); CI = 90; WLI = 179; SBI = 53–55 (54); PSI = 19–21 (20); PWI = 168–215 (191); PLI = 147–196 (171); NI = 124–132 (128); PNWI = 107–135 (121); NLI = 49–52 (50); FI = 230–282 (256).

Gyne description: In full-face view, head subquadrate, slightly longer than broad (CI 90). Mandibles densely, finely 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 strongly convex medially. Antennal scapes short: when fully retracted, failing to reach the posterior margin of the head capsule by about twice the maximum scape width (SI 79–81). Antennae 12-segmented; antennal club composed of three segments, with the apical-most segment about twice as long as the preceding two in combination. Frontal carinae short, extending past the antennal toruli by about 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, converging from below the compound eyes to the mandibular insertions. Posterior head margin flat, rounding evenly into the lateral margins.

In profile view, compound eyes ovular and large (OI 32–33), with 16 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. Posterior margin of metanotum extending 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 moderately well developed, but short (PSI ~ 20), about a third as long as the propodeal declivity, flared at the base, triangular, and acute. Propodeal declivity straight and flat, forming a ~120 ° 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 moderately long (PLI 147–196), without tubercles anterodorsally. Subpetiolar process in the form of a moderately large, triangular, blunt tooth, which grades evenly into the ventral margin of the petiole posteriorly. Petiolar peduncle moderately long: comprising about half of the total petiole length. Petiolar node erect and squamiform: transition between peduncle and node a rounded ~130 ° angle; anterior face forming a ~90 ° angle with the brief dorsal face; dorsal face meeting the posterior face at a ~90 ° angle; posterior face forms a ~90 ° angle with the caudal cylinder. Postpetiole flat anteriorly, bulging slightly anterodorsally, flattened posterodorsally; ventral surface weakly lobed.

In dorsal view, mesoscutum covering pronotum anteriorly, but humeri visible laterally as angulate sclerites. Propodeal spines parallel 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 transversely campaniform: rounded anteriorly and flattened posteriorly; subquadrate when viewed posterodorsally, the dorsum of the node weakly convex. Petiolar node slightly broader than the peduncle and caudal cylinder. Postpetiole moderately broad (PWI 168–215), anteroposteriorly compressed, and subtrapezoidal, articulating with most of the anterior margin of the gaster, leaving small, angulate margins on each side exposed. Anterior margin of postpetiole flat, with corners marked by rounded angles as it transitions to the lateral margins, which converge slightly to the angulate posterior corners; posterior margin flat. Metafemur weakly to moderately incrassate (FI 230–282).

Sculpture: median clypeal carina present, extending from the anterior margin nearly to frontal triangle, and flanked by two weaker, indistinct carinae. Lateral clypeal lobes with additional weaker carinae; ground sculpture weakly areolate. Antennal scapes weakly areolate. Cephalic dorsum areolate, with weak costulae overlying the ground sculpture. Lateral surfaces of head areolate, with fine costulae between the compound eye and mandibular insertion. Ventral surface of head smooth and shining, with weak costulae. Pronotal neck and anterior face of pronotum areolate. Pronotum with areolate ground sculpture arranged into longitudinal rows by superficial costulae. Katepisternum shining medially, otherwise weakly areolate. Anepisternum areolate. Metapleurae and lateral face of propodeum areolate, with costulae that become stronger over the metapleural gland bulla. Propodeal declivity areolate. Mesoscutum predominantly with costulae over areolate ground sculpture; a patch of smooth and shining sculpture anteromedially. Mesoscutellum with costulae over areolate ground sculpture. Femora shining, with traces of weak areolate sculpture. Petiole and postpetiole uniformly areolate, but sculpture becomes weaker on the anterior face of the petiolar node and anterior face of postpetiole. 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 sparse, erect, blunt-tipped, nearly 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 lightly colored integument.

Color: predominantly yellow; with antennae, dorsomedial surface of head, posteromedial surface of mesoscutum, metanotum, propodeal declivity, caudal cylinder of the petiole, caudal cylinder of the postpetiole, and distal quarters of the gastral sclerites testaceous yellow. Wing bases and masticatory margin of mandibles dark brown.

Male: Unknown.

Etymology: Behavioural, from the Latin ‘terra’ (= earth) + ‘genus’ (= born), presumably a reference to the terrestrial nesting and foraging habits of this species.

Comments: Temnothorax terrigena , which inhabits a range from the Chisos Mountains in southwestern Texas through central Texas, and south to Tamaulipas state in Mexico, apparently inhabits a broad range of habitats, including pinyon forests, desert canyons, high Douglas fir/pine forests, and semiarid plains ( van Pelt, 1983, Wheeler, 1903a). It is common in the type locality of Austin, Texas, where it has been collected in litter samples at the Brackenridge Field Laboratory ( Feener, 1981). In the original description ( Wheeler, 1903b), T. terrigena was noted as nesting under stones in black clay soil. Wheeler (1903b) observed workers foraging diurnally and that this species may possibly be pleisiobiotic with other myrmicines: Wheeler collected a nest from a midden pile of the fungus farming ant Mycetomoellerius turrifex (Wheeler) , and another from a Pheidole tepicana Pergande colony. The references to T. terrigena from Hidalgo state by Hernández & Castaño-Meneses (2010), Hernández (2013), Vásquez-Bolaños (2015) are incorrect: the exemplar specimen from the study by Hernández & Castaño-Meneses deposited in the UNAM collection proved to be an undescribed species of the tricarinatus species group (sensu Mackay, 2000) upon examination.

Figures

Figure 170 Temnothorax terrigena. (A–C) Lectotype worker (MCZENT00522078). (A) Full-face view. (B) Profile view. (C) Dorsal view. (D–F) Paralectotype gyne (MCZENT00522078). (D) Full-face view. (E) Profile view. (F) Dorsal view. (G) Geographical and elevational distribution of specimens examined. Type locality is represented by a triangle, non-type localities are represented by circles. Bounding box in inset map shows location of main map. Scale bars 0.2 mm. Full-size DOI: 10.7717/peerj.11514/fig-170