Temnothorax magnabulla

Temnothorax magnabulla is known only from two collections made from the island of St. Croix in the U.S. Virgin Islands. St. Croix receives substantially more precipitation on the western part of the island, with the eastern end dominated by xerophytic scrub; the two collections were made at the extreme eastern and western ends of the island. The biology of this species is unknown but is likely to be similar to other members of the Antillean, terricolous pulchellus group. (Prebus 2021)

Identification
Prebus (2021) – A member of the  pulchellus species group of the Temnothorax salvini clade.

This species is closely related to other terricolous Antillean species, namely Temnothorax albispinus, Temnothorax wettereri, Temnothorax pulchellus, Temnothorax harlequina, and Temnothorax laticrus.

Temnothorax magnabulla can be separated from all other species in the salvini clade by the following character combination: dorsum of head smooth and shining; in profile view, dorsum of mesosoma not strongly convex; pronotal declivity indistinct; metanotal groove not impressed; propodeum not depressed below the level of the promesonotum; propodeum bearing standing setae dorsally; propodeal spines about as long as the propodeal declivity, directed posterodorsally, and straight; hind femora weakly to moderately incrassate; petiolar node flat and relatively short dorsally; transition of dorsal to posterior face of petiolar node evenly rounded; in dorsal view, apex of petiolar node narrower or the same width as the caudal cylinder of the petiole; postpetiole very broad: greater than or equal to 2.4 times the width of the petiole; petiolar node with four erect setae dorsally; setae on head, mesosoma, waist segments and gaster erect, moderately long, sparse and blunt (never long and tapering); integument predominantly yellow: head (except for the mandibles), mesosoma, and gaster are mostly testaceous yellow, with the posterior margins of the gastral sclerites medium brown; coxae, legs, and mandibles are pale yellow.

Similar species: Temnothorax agavicola, Temnothorax ciferrii, Temnothorax flavidulus, Temnothorax harlequina, Temnothorax hippolyta, Temnothorax pulchellus and Temnothorax terricola. The erect setae count of four on the dorsum of the petiolar node differentiates T. magnabulla from T. terricola and T. hippolyta, which have only two along the posterior margin. The flat relatively small compound eyes, with eleven ommatidia in the longest row, and darker yellow integument separate T. magnabulla from T. flavidulus, which has twelve ommatidia in the longest row of the compound eye and is uniformly light yellow. The presence of erect setae on the propodeum distinguishes T. magnabulla from T. pulchellus. The weakly convex dorsal margin of the mesosoma and rounded transition between the dorsal and posterior faces of the petiolar node distinguishes T. magnabulla from T. flavidulus, T. ciferrii, and T. harlequina, in which the mesosoma is strongly convex and the petiolar node transition is angulate. Temnothorax magnabulla and T. harlequina can be separated most easily by the color of the integument: T. harlequina has a light yellow gaster, which contrasts with a darker mesosoma and head, whereas T. magnabulla is uniformly yellow. Temnothorax magnabulla may also be confused with T. agavicola but the head sculpture of this species is areolate, in contrast the smooth and shining sculpture of T. magnabulla

Distribution based on Regional Taxon Lists
Neotropical Region: United States Virgin Islands.

Nomenclature

 * . Temnothorax magnabulla Prebus, 2021: 313, figs. 133J, 144 (w.) VIRGIN IS (St Croix I.).

Worker
(n = 4): SL = 0.458-0.533 (0.507); FRS = 0.182-0.215 (0.199); CW = 0.555-0.642 (0.607); CWb = 0.507-0.591 (0.557); PoOC = 0.238-0.261 (0.252); CL = 0.583-0.667 (0.636); EL = 0.119-0.150 (0.140); EW = 0.091-0.118 (0.107); MD = 0.147-0.165 (0.154); WL = 0.638-0.760 (0.719); SPST = 0.203-0.243 (0.228); MPST = 0.207-0.233 (0.223); PEL = 0.293-0.336 (0.321); NOL = 0.163-0.203 (0.180); NOH = 0.110-0.126 (0.120); PEH = 0.187-0.219 (0.207); PPL = 0.182-0.217 (0.199); PPH = 0.213-0.264 (0.235); PW = 0.340-0.394 (0.379); SBPA = 0.140-0.182 (0.162); SPTI = 0.191-0.239 (0.219); PEW = 0.135-0.164 (0.153); PNW = 0.130-0.164 (0.151); PPW = 0.327-0.393 (0.367); HFL = 0.454-0.508 (0.494); HFWmax = 0.122-0.159 (0.142); HFWmin = 0.042-0.061 (0.053); CS = 0.799-0.925 (0.875); ES = 0.165-0.209 (0.194); SI = 90-92 (91); OI = 21-23 (22); CI = 87-89 (88); WLI = 126-132 (129); SBI = 27-32 (29); PSI = 31-32 (32); PWI = 237-242 (239); PLI = 149-170 (162); NI = 139-161 (151); PNWI = 96-100 (98); NLI = 50-60 (56); FI = 251-290 (270).

In full-face view, head subquadrate, slightly longer than broad (CI 87-89). Mandibles weakly striate, shining, and armed with five teeth: the apical-most well developed, followed by a smaller preapical tooth, which is followed by three equally developed smaller teeth. Anterior clypeal margin entire and evenly convex. Antennal scapes moderately long: when fully retracted, extending past the posterior margin of the head capsule by about the maximum width of the scape (SI 90-92). Antennae 12- segmented; antennal club of three segments, with the apical-most segment slightly longer than the preceding two in combination. Frontal carinae short, extending past the antennal toruli by 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 evenly convex, forming a continuous arc from the posterior of the head to the mandibular insertions. Posterior head margin slightly convex, rounding evenly into the lateral margins.

In profile view, compound eyes ovular and moderately large (OI 21-23), with 11 ommatidia in longest row. Pronotal declivity indistinct, neck and anterior face of pronotum forming a rounded ~130° angle. Mesosoma convex dorsally, but flatter on the propodeum. Promesonotal suture extending from the posterior margin of the procoxal insertion only to the mesothoracic spiracle, which is well developed. Metanotal groove barely visible dorsally as a slight indentation and disruption of the weak sculpture. Propodeal spiracle well developed, directed posterolaterally, and separated from the propodeal declivity by about three spiracle diameters. Propodeal spines well developed and moderately long (PSI 31-32), about as long as the propodeal declivity, straight, tapering evenly from the base, and acute. Propodeal declivity straight and flat, forming a rounded ~90° angle with the base of the propodeal spines. Propodeal lobes rounded and very weakly developed. Metapleural gland bulla large, extending from the metacoxal insertion three quarters of the way to the propodeal spiracle. Petiole moderately long (PLI 149-170), without tubercles anterodorsally where it articulates with the mesosoma. 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 very slightly concave posterior to the process. Petiolar peduncle moderately long: comprising about half the total length of the petiole. Petiolar node robust and erect: transition between peduncle and node marked by a rounded angle of ~120°, resulting in a concave anterior node face; anterior face forming a rounded ~90° angle with the dorsal face, which is evenly convex and moderately long; dorsal face rounding evenly into the posterior face, which forms a ~120° angle with the caudal cylinder. Postpetiole evenly rounded dorsally; weakly lobed ventrally.

In dorsal view, humeri weakly developed: rounded and only slightly protruding past 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. Mesonotum and propodeum separated by a very weak depression, their margins converging evenly to the bases of the propodeal spines. Propodeal spines broadly approximate basally and diverging apically, their apices separated from each other by slightly more than their length; negative space between them a basally narrowed "U". Petiolar peduncle with spiracles protruding past lateral margins, peduncle constricted anterior to them. Petiolar node campaniform: narrowest anteriorly, flat posteriorly, with the posterior corners rounded; slightly wider than the peduncle, evenly grading into the caudal cylinder, which is slightly wider than the node. Postpetiole very broad (PWI 237-242) and campaniform, articulating with nearly the entire anterior margin of the gaster. Anterior margin of the postpetiole flat, with the corners evenly rounding into the lateral margins, which evenly diverge to the angulate posterior corners; posterior margin broadly concave. Metafemur moderately incrassate (FI 251-290).

Sculpture: median clypeal carina present, but very weak: barely visible against the smooth and shining ground sculpture, flanked by additional slightly stronger carinae. Antennal scapes shining through very weak, indistinct ground sculpture. Cephalic dorsum predominantly smooth and shining, with weak costulae medial to the frontal carinae, faint areolate sculpture surrounding the compound eyes, and weak areolate sculpture on the posterolateral margins of the head. Pronotal neck areolate. Mesosoma predominantly smooth and shining, with weak areolate sculpture and rugulae present on the lateral margins of the pronotum, meso-, and metapleurae; dorsally, predominantly weakly areolate, with weak costulae present on the pronotum; mesonotum with weaker sculpture than the rest of the mesosoma. Femora shining through very weak traces of areolate sculpture. Petiole with very shallow areolate sculpture on most surfaces, but petiolar node smooth and shining dorsally. Dorsal surface of postpetiole smooth and shining, with weak areolate sculpture on the posterior quarter. Gaster smooth and shining, without spectral iridescence. Surface of the first gastral sternite smooth and shining.

Setae: antennal scapes and funiculus with short, adpressed pilosity. Dorsum of head, pronotum, waist segments and gaster with sparse, short, erect, blunt-tipped setae, the longest of which are slightly less than the length of the compound eye. The head bears ~20, mesosoma ~10, petiole 4, postpetiole ~6, and first gastral tergite ~10 setae. Sparse, adpressed, very short pubescence present on the entire body, but nearly undetectable against the lightly colored integument.

Color: head (except for the mandibles), mesosoma, and gaster are mostly testaceous yellow, with the posterior margins of the gastral sclerites medium brown. Coxae, legs, and mandibles are pale yellow.

Type Material
Holotype worker: U.S. VIRGIN ISLANDS: St. Croix: Knight: Routes 60 & 82,, 31 October 2005, J.K. Wetterer #160 (CASENT0756093).

Paratype workers: U.S. VIRGIN ISLANDS: St. Croix: same data as holotype, 1 worker (CASENT0758673) 1 worker (LACMENT323205).

Etymology
Morphological, from the Latin ʻmagna' (= large) + bulla (= bubble-like cavity), in reference to the enlarged metapleural gland bulla.