Strumigenys aello

Identification
Bolton (2000) - This minute species is very distinctive and easily separated from all other members of the group. It lacks a sharply defined transverse crest across the highest point of the vertex and has two transverse rows of erect hairs on the head. It is related to Strumigenys acheron, both species having an evenly rounded leading edge to the scape (rather than being distinctly angular), and each possesses both cephalic and pronotal standing pilosity. However, acheron has only a single row of hairs across the vertex, has a sharply defined transverse crest across the head, and has more than a single ommatidium in the eye.

More widely in the group aello separates from Strumigenys deinognatha and Strumigenys extemena as the last two have mandibles whose dorsal surfaces are oblique and slope strongly downward from the masticatory to the outer margins, and the unique structures of the mandibular dorsum in Strumigenys tarbosyne, Strumigenys carinognatha and Strumigenys atopogenys immediately isolate these three species. Both Strumigenys ocypete and Strumigenys podarge have an anteriorly projecting hair at the broadest point of the scape that is shaped distinctly differently from other hairs on the leading edge, whereas in aello all hairs on the leading edge of the scape are of the same shape, varying only in size.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Indonesia, Malaysia.

Nomenclature

 *  aello. Pyramica aello Bolton, 2000: 416 (w.) BORNEO. Combination in Strumigenys: Baroni Urbani & De Andrade, 2007: 115

Worker
Holotype. TL 1.5, HL 0.39, HW 0.36, CI 92, ML 0.12, MI 31, SL 0.18, SI 50, PW 0.22, AL 0.42. Leading edge of scape rounded at its broadest point, the edge with a continuous row of small, apically curved spatulate to spoon-shaped hairs that decrease in size toward the apex; without a freely anteriorly projecting specialised hair of markedly different shape at the broadest point of the scape. Basal tooth of mandible triangular and distinctly the largest on the visible margin. Dorsum of head in profile narrowly rounded at its highest point but without a distinctly defined ridge or crest that traverses the vertex at its broadest point. Vertex with a transverse row of 4 short erect straight hairs at its highest point, and with a second transverse row of 4 similar hairs between the highest point and the occipital margin; head otherwise without erect hairs. Eye of a single ommatidium. Median area of clypeus more or less smooth, head behind clypeus finely punctulate-granular. Pronotum with a straight humeral hair on each side, the mesonotum with an anteriorly situated pair of short erect hairs. Petiole, postpetiole and first gastral tergite with straight simple hairs that are erect to suberect. Legs only with minute appressed spatulate hairs that are directed toward the apices. Pronotal dorsum mostly shining between the dorsolateral marginations, with only extremely feeble sculpture; propodeum mostly smooth dorsally. Pleurae and side of propodeum mostly smooth except near dorsal outline where faint sculpture is present. Propodeal declivity with broad lamellae. Petiole node broader than long in dorsal view, it and the postpetiole unsculptured.

Type Material
Holotype worker, Malaysia: Sarawak, 4th. Division, Gn. Mulu Nat. Pk RGS Expd., Long Pala, 18.x.1977, lowl. rainfor. leaf litter (B. Bolton).