Stereomyrmex dispar

Stereomyrmex dispar was described from a unique worker taken in 1933 on remote Bellona Island (11°20’S; 159°47’E), south of Guadalcanal, Solomon Islands (Wheeler, 1934).

Distribution based on Regional Taxon Lists
Indo-Australian Region: Solomon Islands.

Nomenclature

 *  dispar. Willowsiella dispar Wheeler, W.M. 1934a: 175, fig. 1 (w.) SOLOMON IS. Combination in Stereomyrmex: Bolton, 2003: 273.

Worker
Length very nearly 2.5 mm.

Head trapezoidal, slightly longer than broad, with nearly straight, anteriorly converging sides and feebly and evenly convex posterior border; in profile moderately convex above and subtruncate behind, with concave occipital border. Eyes slightly in front of the middle of the sides, moderately large, convex, semicircular, with straight inferior orbit. Mandibles with straight external borders and two or three blunt teeth in addition to the acute apical tooth. Antennal scapes reaching to the posterior fourth of the head, curved at their bases; first funicular joint one and one-half times as long as broad; joints 2-7 fully twice as broad as long; eighth nearly as long as the three preceding joints• together; the ninth as long as broad, the terminal distinctly longer than the combined eighth and ninth. Thorax in profile convex and evenly rounded above; seen from above slightly more than twice as long as broad, broader in front than behind, with broadly arcuate anterior border, subrectangular humeri and straight sides which gradually converge posteriorly to the epinotal region where they become subparallel. Epinotal spines as broad at the base as long, acute, strongly compressed, subparallel, directed backward and slightly upward, the space between them sloping and feebly concave. Petiolar node in profile higher than long, truncated anteriorly and posteriorly and rounded dorsally; seen from above transversely subelliptical, broader than the epinotum, with very bluntly angulate sides, nearly one and one-half times as broad as long. The peduncle bears on each side a blunt rectangular projection and at its anteroventral border a blunt tooth. Postpetiole anteroposteriorly compressed and cuneate in profile, with straight anterior and posterior surfaces and blunt superior border; from above much narrower than the petiolar node, broadly trapezoidal, fully twice as broad as long, its anterior and lateral borders straight, the latter strongly converging posteriorly. First gastric segment subquadrate, with broadly rounded anterior and posterior corners and deeply excised anterior border.

Shining; body and legs regularly, very finely and delicately reticulate, with sparse umbilicate punctures, distinctly coarser on the mandibles, head, thorax and petiole than on the postpetiole and gaster, which are smoother and more minutely and sparsely punctate. Frontal carinae and clypeus granular, the raised median portion of the latter with a few longitudinal rugae on each side. Cheeks coarsely reticulate-rugose; lower portion of epinotal declivity with several transverse rugae.

Hairs yellowish, very short, erect only on the clypeus and tip of the gaster, elsewhere appressed and arising from the umbilicate punctures. Pubescence short, even, appressed, confined to the antennae and legs.

Black; mandibles, antennae, legs and terminal segments of gaster yellowish brown; femora dark brown, except at their bases and tips; median portion of antennal scapes somewhat infuscated.

Taylor (1991) - TL ca. 3.2; HL 0.79; HW (across eyes) 0.72, (maximum behind eyes) 0.69; CI 87; SL 0.53; SI 77; PW 0.59; WL 1.00; midline length of petiolar node 0.38; petiolar node width 0.52; midline length of postpetiole 0.24; postpetiole width 0.43.

Type Material
Described from a single specimen taken by Mr. Maurice Willows Jr. at the northwestern end of Bellona Island, Solomons (VI.23.33).

Taylor (1991) - The holotype (California Academy of Sciences, San Francisco) is mounted on 2 points, one with the head, mesosoma and petiole, the other with the postpetiole and gaster. It carries a small red tag with the words “HOLOTYPE” (printed) and “W. dispar”(hand-written); a large label reading “Willowsiella dispar Wheeler (Type)” in Wheeler’s handwriting; and four small printed white data labels, reading respectively: “Solomon Islands”; “NW end of Bellona Isd, VI 23-33”; “M. Willows Jr. Collector”; and “Templeton Crocker Exped. 1933”.