Temnothorax nigricans ( 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 : 210-216

Temnothorax nigricans ( Baroni Urbani, 1978)

Distribution: Fig. 121B ; worker & gyne: Fig. 123 .

Macromischa melanocephala Wheeler, 1931: 15 . Syntype workers and gynes. Ensenada de Cochinos , Cuba. One syntype worker here designated lectotype.

Leptothorax nigricans: Baroni Urbani, 1978: 467 . Transfer to Leptothorax . Nomen novum for Leptothorax melanocephalum (Wheeler) (nec Leptothorax melanocephalum Emery, 1870: 197 ).

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

Type material examined: Lectotype worker: CUBA: Artemisia: Hacienda Jiqui, Ensenada de Cochinos, 5 October 1929, J.G. Myers #C250, nest in fallen mahogany fruit, M.C.Z. Cotype 16365 (MCZENT00577110, middle specimen on pin) [ MCZC].

Paralectotype workers and gynes: same pin as lectotype, 2 workers (top and bottom specimens on pin) [ MCZC]; same data as lectotype, 3 workers (MCZENT00577111) [ MCZC] 2 workers (MCZENT00577112) [ MCZC] 2 dealate gynes (MCZENT00577113) [ MCZC] 3 workers (MCZENT00577114) [ MCZC] 3 workers (MCZENT00016365) [ MCZC] 3 workers (CASENT0758264) [ USNM] 3 workers (CASENT0758265) [ USNM] 1 worker (images of CASENT0915381 examined on antweb.org) [ MNHN] .

Geographic range: Low elevations of Cuba (Artemisia) ( Fig. 121B ).

Worker diagnosis: Temnothorax nigricans can be separated from all other species in the salvini clade by the following character combination: antennal scapes very long, surpassing the posterior margin of head by about one and a half times the maximum width of the antennal scape (SI 92–100); anterior margin of clypeus entire; transition between anterior and dorsal faces of pronotum continuous, not marked by a transition or a weak transverse carina; in profile view, mesosoma strongly convex dorsally and compact (WLI 122–132); in dorsal view, mesosoma posterior to the pronotum swollen, only slightly narrower than the pronotum; dorsum of propodeum with setae; in dorsal view, propodeal spines broadly approximated basally, negative space between them “U” shaped; propodeal spines about as long as the propodeal declivity, directed posterodorsally, and weakly downcurved; hind femora weakly to moderately incrassate (FI 224–291); petiolar node weakly squamiform, dorsally rounded; dorsum of petiole with four erect setae; in dorsal view, petiolar node slightly broader than the caudal cylinder (PNWI <160); postpetiole moderately to very broad (PWI 212–239); dorsum of head uniformly areolate; dorsum of postpetiole with> 10 erect setae; integument bicolored: antennal funiculus, clypeus, and distal third of the femora testaceous yellow; head capsule dark brown; mandibles, mesosoma, legs, waist segments, and gaster light yellow.

Similar species: Temnothorax misomoschus sp. nov., T. subditivus , and other members of the pastinifer group. Temnothorax nigricans can be distinguished from T. subditivus by the narrower petiolar node in dorsal view (PNWI <160 vs.> 160 in T. subditivus ), the somewhat shorter petiolar peduncle (~2/3 of the total petiole length in T. nigricans vs. ~ 3/ 4 in T. subditivus ) and the sculpture of the head dorsum (uniformly areolate in T. nigricans vs. variable in T. subditivus , but never uniformly areolate). In contrast to T. nigricans , T. misomoschus sp. nov. is devoid of erect setae on most surfaces of the body, has a depressed propodeum, and a posteriorly leaning, subquadrate petiolar node. Temnothorax nigricans can be separated from other members of the pastinifer group by the areolate head (smooth and shining in T. schwarzi ), weakly convex anterior clypeus margin (strongly emarginate in T. pastinifer ), moderately long antennal scape, which surpasses the posterior margin of the head by about one and a half times the maximum width of the antennal scape (barely surpassing the posterior margin in T. androsanus ), the continuous transition between the anterior and dorsal faces of the pronotum in profile view (transition distinct in T. androsanus ). Temnothorax nigricans can also be separated from T. rutabulafer sp. nov. by the relatively narrow petiolar node in dorsal view (PNWI 130–149 vs.> 180 in T. rutabulafer sp. nov.).

Worker measurements & indices (n = 7): SL = 0.454 –0.512 (0.477); FRS = 0.169 –0.189 (0.179); CW = 0.502 –0.573 (0.537); CWb = 0.452 –0.524 (0.489); PoOC = 0.211 –0.237 (0.226); CL = 0.532 –0.602 (0.570); EL = 0.115 –0.131 (0.123); EW = 0.090 –0.104 (0.097); MD = 0.135 –0.154 (0.142); WL = 0.574 –0.667 (0.619); SPST = 0.244 –0.289 (0.263); MPST = 0.192 –0.233 (0.213); PEL = 0.212 –0.278 (0.248); NOL = 0.131 –0.177 (0.149); NOH = 0.105 –0.141 (0.120); PEH = 0.182 –0.234 (0.210); PPL = 0.131 –0.158 (0.147); PPH = 0.163 –0.198 (0.182); PW = 0.347 –0.393 (0.369); SBPA = 0.143 –0.175 (0.156); SPTI = 0.226 –0.264 (0.244); PEW = 0.110 –0.142 (0.124); PNW = 0.154 –0.189 (0.173); PPW = 0.259 –0.303 (0.283); HFL = 0.419 –0.491 (0.465); HFWmax = 0.122 –0.153 (0.136); HFWmin = 0.047 –0.059 (0.054); CS = 0.718 –0.825 (0.774); ES = 0.160 –0.183 (0.172); SI = 92–100 (98); OI = 22–23 (22); CI = 84–89 (86); WLI = 122–132 (127); SBI = 30–35 (32); PSI = 41–45 (42); PWI = 212–239 (229); PLI = 159–180 (168); NI = 115–131 (124); PNWI = 130–149 (140); NLI = 55–71 (60); FI = 224–291 (254).

Worker description: In full-face view, head subquadrate, longer than broad (CI 84–89). Mandibles finely striate, 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 flat to evenly convex medially. Antennal scapes very long: when fully retracted, surpassing the posterior margin of the head capsule by about one and a half times the maximum width of the antennal scape (SI 92–100). Antennae 12-segmented; antennal club of three segments, with the apical-most segment longer than 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. Lateral margin of head weakly convex, converging evenly to the mandibular insertions. Posterior head margin flat to very slightly concave, rounding evenly into the lateral margins.

In profile view, compound eyes ovular and moderately large (OI 22–23), with 12 ommatidia in longest row. Pronotal declivity indistinct, but pronotal neck and anterior face of pronotum forming a rounded ~120 ° angle. Mesosoma evenly, but weakly, convex dorsally 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 moderately well developed. Metanotal groove nearly entirely absent: only visible as a faint disruption in the surface sculpture between meso- and metacoxal insertions to the minute metathoracic spiracle, which is indistinguishable from the ground sculpture. Propodeal spiracle well developed, directed posterolaterally, and separated from the propodeal declivity by about two and a half spiracle diameters. Propodeal spines well developed and long (PSI 41–45), longer than the propodeal declivity, tapering evenly from the base, downcurved for most of their length but turning up slightly at the tips, and acute. Propodeal declivity weakly concave, forming a rounded ~110 ° angle with the base of the propodeal spines. Propodeal lobes rounded and weakly developed, but with an angulate dorsal flange. Metapleural gland bulla moderately large, extending from the metacoxal insertion two thirds of the way to the propodeal spiracle. Petiole moderately long (PLI 159–180), without tubercles anterodorsally. Subpetiolar process in the form of a weakly developed, acute tooth, which grades evenly into the ventral margin of the petiole posteriorly. Ventral surface of petiole bulging medially. Petiolar peduncle long, comprising about two thirds of the total length of the petiole. Petiolar node squamiform: transition between peduncle and node marked by a rounded angle of ~110 °; anterior face of the node is straight and does not overhang the peduncle; anterior face rounds evenly into the strongly convex dorsal face, which rounds evenly into the posterior face. Postpetiole evenly rounded anterodorsally, before flattening posterodorsally; flat ventrally.

In dorsal view, humeri very weakly developed: rounded and only slightly wider than the rest of the mesosoma; mesothoracic spiracles not protruding past the lateral margins of the mesosoma. Metanotal groove absent: mesonotum and propodeum completely fused and converging evenly to the bases of the propodeal spines. Propodeal spines broadly approximated basally and diverging apically, their apices separated from each other by slightly less than their length; negative space between them a “U”. Petiolar peduncle with spiracles not protruding past the lateral margins. Petiolar node squamiform: rounded anteriorly, with a flattened posterior face, much wider than the peduncle, and narrowing into the caudal cylinder, which is narrower than the node. Postpetiole moderately to very broad (PWI 212–239) and campaniform, articulating with nearly the entire anterior margin of the gaster, but leaving angulate corners of the gaster exposed on each side. Anterior margin of the postpetiole broadly convex, meeting the lateral margins at rounded angles; lateral margins diverging evenly posteriorly; posterior margin flat. Metafemur weakly to moderately incrassate (FI 224–291).

Sculpture: median clypeal carina present, flanked by two slightly weaker carinae over areolate-costulate ground sculpture. Antennal scapes weakly areolate and dull. Cephalic dorsum and lateral surfaces of head with dense areolae arranged into longitudinal rows by costulae; ventral surface shining through weaker areolate sculpture. Pronotal neck areolate. Lateral face of pronotum with sculpture similar to the cephalic dorsum. Lateral face of propodeum, meso- and metapleurae uniformly areolate. Dorsally, mesosoma sculptured similarly to the cephalic dorsum. Areolate sculpture weaker on the propodeal declivity. Femora weakly shining through areolate sculpture. Petiolar peduncle, venter, anterior, and posterior faces of the petiolar node weakly shining through shallow areolate sculpture; dorsal face of the petiolar node more densely areolate. Dorsal surface of postpetiole dull with areolate sculpture and costulae. Gaster smooth and shining, with weak spectral iridescence on the first tergite. Surface of the first gastral sternite smooth and shining.

Setae: antennal scapes and funiculi with short, adpressed pilosity. Dorsum of head, mesosoma, waist segments and gaster with short, erect, blunt-tipped setae, the longest of which are roughly the width of the compound eye. The head bears ~32, mesosoma ~22, petiole 6, postpetiole ~10, and first gastral tergite ~36 setae. Sparse, adpressed pubescence present on the entire body, but may be difficult to discern from the dense ground sculpture and light integument on most of the body.

Color: funiculus of the antenna, clypeus, and distal third of the femora testaceous yellow. Head capsule dark brown. Mandibles, mesosoma, legs, waist segments, and gaster light yellow.

Gyne measurements & indices (n = 2): SL = 0.469 –0.520 (0.495); FRS = 0.212 –0.230 (0.221); CW = 0.637 –0.687 (0.662); CWb = 0.590 –0.646 (0.618); PoOC = 0.245 –0.251 (0.248); CL = 0.627 –0.675 (0.651); EL = 0.173 –0.183 (0.178); EW = 0.132 –0.158 (0.145); MD = 0.155 –0.160 (0.158); WL = 0.903 –1.008 (0.956); SPST = 0.259 –0.269 (0.264); MPST = 0.262 –0.265 (0.264); PEL = 0.287 –0.317 (0.302); NOL = 0.160 –0.175 (0.168); NOH = 0.131 –0.164 (0.148); PEH = 0.257 –0.287 (0.272); PPL = 0.182 –0.187 (0.185); PPH = 0.226 –0.250 (0.238); PW = 0.554 –0.628 (0.591); SBPA = 0.287 –0.345 (0.316); SPTI = 0.273 –0.312 (0.293); PEW = 0.149 –0.174 (0.162); PNW = 0.194 –0.213 (0.204); PPW = 0.371 –0.432 (0.402); HFL = 0.535 –0.589 (0.562); HFWmax = 0.128 –0.144 (0.136); HFWmin = 0.056 –0.059 (0.058); CS = 0.904 –0.984 (0.944); ES = 0.239 –0.262 (0.251); SI = 79–80 (80); OI = 26–27 (27); CI = 94–96 (95); WLI = 153–156 (155); SBI = 49–53 (51); PSI = 27–29 (28); PWI = 248–249 (249); PLI = 153–174 (164); NI = 107–122 (114); PNWI = 122–130 (126); NLI = 55–56 (55); FI = 229–244 (236).

Gyne description: In full-face view, head subquadrate, about as long as broad (CI 94–96). Mandibles densely, finely striate, 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 flat to weakly emarginated medially. Antennal scapes moderately long: when fully retracted, just reaching the posterior margin of the head capsule (SI 79–80). Antennae 12-segmented; antennal club composed of three segments, with the apical-most longer than the preceding two in combination. Frontal carinae moderately long, 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. 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 26–27), with 17 ommatidia in longest row. Mesoscutum rounded evenly anteriorly, barely covering the dorsal surface of the pronotum, and weakly convex dorsally. Mesoscutellum slightly depressed below the level of the mesoscutum. Posterior margin of metanotum extending slightly past the posterior margin of the mesoscutum, the two sclerites form an even convexity. Propodeal spiracle well developed, directed posterolaterally, and separated from the propodeal declivity by about three and a half spiracle diameters. Propodeal spines stout, well developed, and moderately long (PSI 27–29), about as long as the propodeal declivity, tapering evenly from the base, directed posteriorly, straight, and acute. Propodeal declivity weakly concave, forming a rounded ~90 ° angle with the base of the propodeal spines. Propodeal lobes rounded and weakly developed, but with a flange that is slightly angulate dorsally. Metapleural gland bulla moderately large, extending from the metacoxal insertion two thirds of the way to the propodeal spiracle. Petiole moderately long (PLI 153–174), with peduncle evenly rounded anterodorsally. Subpetiolar process in the form of a weakly developed, acute tooth, which grades evenly into the ventral margin of the petiole posteriorly. Petiolar peduncle long, comprising about two thirds of the total length of the petiole. Petiolar node squamiform: transition between peduncle and node marked by a rounded angle of ~120 °; anterior face transitioning joining the short dorsal face at a ~90 ° angle, which rounds evenly into the posterior face. Postpetiole evenly rounded anterodorsally, bulging slightly before it transitions into the flattened dorsal face; ventral surface weakly lobed.

In dorsal view, mesoscutum covering pronotum anteriorly, but humeri visible laterally as rounded sclerites. Propodeal spines weakly diverging basally but parallel apically, their apices separated from each other by about one and a half times their length; negative space between them a broad “U”. Petiolar peduncle with spiracles weakly protruding past the lateral margins. Petiolar node squamiform: flat anteriorly, with lateral faces strongly convex, and with a flattened posterior face, much wider than the peduncle, and narrowing into the caudal cylinder, which is narrower than the node. Postpetiole very broad (PWI 248–249) and campaniform, 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 evenly diverge to the angulate posterior corners; posterior margin flat. Metafemur weakly incrassate (FI 229–244).

Sculpture: median clypeal lobe with about seven equally strong fine carinae, extending from the anterior margin nearly to frontal triangle. Lateral clypeal lobes with additional fine carinae; ground sculpture weakly areolate. Antennal scapes weakly shining through areolate sculpture. Cephalic dorsum and lateral surfaces of head with dense costulae over areolate sculpture; ventral surface shining through weaker areolate-costulate sculpture. Pronotal neck areolate. Pronotum, a posterior two thirds of the anepisternum and katepisternum, and lateral face of the propodeum with sculpture similar to that of the cephalic dorsum, but slightly weaker. Propodeal declivity weakly areolate-costulate. Mesoscutum and mesoscutellum with sculpture similar to that of the cephalic dorsum. Mesoscutellum smooth and shining medially, surrounded by costulae and areolae. Femora shining through weak areolate sculpture. Petiole with weak areolate sculpture on all surfaces, becoming stronger on the dorsoposterior surface of the node. Postpetiole densely areolate dorsally. Gaster predominantly smooth and shining, but with the anterior of the first gastral tergite finely areolate-costulate, and with faint spectral iridescence. Surface of the first gastral sternite smooth and shining.

Setae: antennal scapes and funiculi with short, adpressed pilosity. Dorsum of head, mesosoma, waist segments and gaster with short, erect, blunt-tipped setae, the longest of which are roughly three quarters of the compound eye width. Sparse, adpressed pubescence present on the entire body, but may be difficult to discern from the dense ground sculpture and light integument on most of the body.

Color: funiculus of the antenna, clypeus, and distal third of the femora testaceous yellow. Meso- and metapleurae, anteromedial and posterolateral portions of the mesoscutum, posterior edge of the mesoscutellum, metanotum, and posterior third of all gastral sclerites testaceous. Head capsule dark brown. Mandibles, mesosoma, legs, waist segments, and gaster light yellow.

Male: Unknown.

Etymology: Morphological, from the Latin ‘nigricans’ (= blackish), presumably in reference to the dark head.

Comments: In the original description by Wheeler (1931), the type series of Temnothorax nigricans was collected from the ground in a fruit of Swietenia mahogani , a hardwood species endemic to the Caribbean islands and southern Florida. The type locality is in northern Artemisia province on the west side of Cuba, which experiences a dry season typical of many islands in the Caribbean but receives substantial precipitation year-round, leading to this area being classified as having a tropical rainforest climate. In addition to the type locality, this species has been reported from numerous other localities across the island by Alayo (1974), including Ciénaga de Zapata, Cienfuegos, Caibarién, Buenos Aires, Escambray, and Seibabo. I have only been able to examine the original nest series, but the presence of multiple gynes suggests that this species may be polygynous. In his remarks on this species, Wheeler (1931) mused about the resemblance of the structure of the mesosoma to Antillaemyrmex Mann (a now defunct genus applied to what is presently referred to as the pulchellus group + T. allardycei (Mann)) and in petiolar shape to Macromischa (probably referring T. pastinifer ). Our current understanding is that Macromischa , as defined by Mann (1920) with T. purpuratus (Roger) as the type for the genus, is polyphyletic: namely T. subditivus , T. androsanus , T. pastinifer , T. fuscatus , and T. salvini are all more closely related to T. terricola than they are to T. purpuratus (see Prebus, 2017), mostly concurring with Fontenla Rizo (2000), which inferred phylogenetic relationships within Temnothorax using morphology.

Figures

Figure 121 Geographical and elevational distribution of the pastinifer group. (A) Temnothorax androsanus (B) T. nigricans (C) T. pastinifer (D) T. rutabulafer sp. nov. (E) T. schwarzi. 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; if present, types of synonyms are named; 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-121

Figure 123 Temnothorax nigricans. (A–C) Lectotype worker (MCZENT00577111). (A) Full-face. (B) Profile view. (C) Dorsal view. (D–F) Paralectotype gyne (MCZENT00577113). (D) Full-face. (E) Profile view. (F) Dorsal view. Scale bars 0.2 mm. Full-size DOI: 10.7717/peerj.11514/fig-123