Strumigenys arnoldi

Identification
Bolton (1983) - Within the arnoldi-complex the species Strumigenys tetraphanes, Strumigenys korahyla, Strumigenys arnoldi and Strumigenys omalyx are characterized by lacking pronotal flagellate hairs whilst retaining the usual mandibular dentition of 2 preapical teeth on each blade. Of the four tetraphanes is instantly recognized by its short broad head and enormous plate-like lobate extension of the antennal scapes. S. korahyla has long narrow mandibles and scapes (MI 48-50, SI 82-85), and has the scapes evenly tapering from base to apex. S. arnoldi is separated from omalyx by details of sculpture as in the latter the sides of the pronotum and the postpetiolar disc are strongly sculptured, and the reticulate-punctate sculpture of the pronotal dorsum is not overlaid by longitudinal rugulae. In arnoldi, on the other hand, the pronotal sides and postpetiolar disc are smooth, and the pronotal dorsum has longitudinal rugulae overlying the reticulate-punctate sculpture.

Distribution based on Regional Taxon Lists
Afrotropical Region: Kenya, United Republic of Tanzania, Zimbabwe.

Nomenclature

 *  arnoldi. Strumigenys arnoldi Forel, 1913a: 114 (w.) ZIMBABWE. See also: Brown, 1954k: 26; Bolton, 1983: 365; Bolton, 2000: 591.

Worker
TL 2.0-2.1, HL 0.54-0.60, HW 0.39-0.46, CI 74-78, ML 0.22-0.23, MI 38-41, SL0.30-0.32, SI 68-75, PW 0.24-0.26, AL 0.54-0.58 (3 measured).

Mandibles in full-face view broadest near the base and gradually tapering towards the apex. Apical fork of each mandible with 2 spiniform teeth, without intercalary teeth or denticles. Pre apical armament of each mandibular blade of 2 teeth, the proximal pre apical much longer than the distal and the distance separating their bases less than the height of the distal preapical tooth. Both pre apical teeth situated in the apical third of the length of the blade. Upper scrobe margins forming a feeble rim or flange, the eyes not visible in full-face view. Eyes small, the maximum diameter distinctly less than the maximum width of the scape. Preocular notch absent, the ventral surface of the head without a preocular transverse impression or groove on each side. Antennal scapes shallowly curved in the basal third, the leading edges weakly convex and equipped with a row of apically curved spoon-shaped hairs which are about the same size as those fringing the upper scrobe margins. Dorsum of head with dense anteriorly curved hairs which are scale-like to stud-like in full-face view, the upper scrobe margins fringed with similar hairs. Dorsum of head everywhere finely and densely reticulate-punctate. Pronotal humeri without flagellate hairs. Mesonotum with a single pair of stout standing hairs. Ground-pilosity of dorsal alitrunk like that of cephalic dorsum but the hairs tending to be smaller and sparser. Posterior portion of mesonotum depressed, the metanotal groove absent. Propodeal teeth broadly triangular and conspicuous, subtended by broad sinuate infradental lamellae. Sides of alitrunk smooth except for some punctures on the upper portion of the mesopleuron. Entire dorsal alitrunk finely reticulate-punctate, on the pronotum this sculpture overlaid by some fine longitudinal rugulation. Dorsum of petiole node finely punctate, the postpetiolar disc smooth and shining. Spongiform appendages of pedicel segments well developed, the petiole with a broad ventral strip which has its ventral free margin indented before the midlength. Ventral spongiform lobe of postpetiole larger than the exposed area of the postpetiolar disc in profile and distinctly larger than the lateral spongiform lobe. Basigastral costulae short and sparse, widely spaced on each side of a broad central clear area. Petiole, postpetiole and first gastral tergite with stout standing hairs which are swollen to clavate apically. Colour dull yellow.

Type Material
Holotype worker, ZIMBABWE: Bulawayo, under stone in nest of Bothroponera krugeri (Forel) (G. Arnold) [examined].