Strumigenys chyatha

Known from the holotype, collected from cocoa leaf litter.

Identification
Bolton (2000) - A member of the chyatha complex in the Strumigenys emarginata  group. Characters of chyatha-complex. Suborbicular hairs present on head in a transverse band of 3 rows immediately in front of the occipital margin; absent anterior to this. Head markedly dorsoventrally flattened (maximum depth 0.60 X HW). Cephalic dorsum, alitrunk, waist segments and first gastral tergite without standing hairs.

Bolton (1983) - Along with Strumigenys impidora in the emarginata-group chyatha shares the characters of strongly reduced pilosity and markedly dorsoventrally flattened head, where the maximum depth of the head is 0·60 x HW and the posteroventral convexity of the surface is vestigial. The retention by chyatha of some suborbicular hairs on the cephalic dorsum links this species with Strumigenys behasyla, Strumigenys sharra and Strumigenys cavinasis, where these specialized hairs are much better developed. In the worker chyatha and impidora are easily separated as the former has a row of adherent sub orbicular hairs lining the upper scrobe margins and has a transverse band of suborbicular hairs on the cephalic dorsum between the vertex and the occipital margin. Such suborbicular hairs are absent in impidora.

Distribution based on Regional Taxon Lists
Afrotropical Region: Ghana.

Nomenclature

 *  chyatha. Smithistruma chyatha Bolton, 1983: 288, fig. 5 (w.) GHANA. Combination in Pyramica: Bolton, 1999: 1673; in Strumigenys: Baroni Urbani & De Andrade, 2007: 117. See also: Bolton, 2000: 301.

Worker
Holotype. TL 2.1, HL 0.62, HW 0.39, CI 63, ML 0.08, MI 13, SL 0.25, SI 64, PW 0.24, AL 0.59.

Mandibles with 5 relatively large teeth followed by two slightly smaller teeth, 4 denticles and an apical small tooth. Basal lamella concealed by clypeus. Anterior clypeal margin broadly and evenly concave, equipped with a row of 7 scale-like hairs which project forward over the mandibles. Of the seven the three central hairs are the smallest, the next one on each side is slightly larger and the outermost on each side (closest to the anterolateral angle) is much larger, transitional in size and shape to the continuous fringe of spatulate anteriorly curved long hairs which project from the lateral clypeal margins. Upper scrobe margins with a single row of adherent suborbicular hairs. Dorsum of head between highest point of vertex and occipital margin with suborbicular hairs present in a transverse band. Remainder of cephalic dorsum and clypeal dorsum without hairs, equipped only with minute pubescence which is somewhat flattened and is only visible under very high magnification. Flagellate hairs absent. Lateral margins of clypeus shallowly convex and convergent anteriorly, the preocular laminae slightly divergent anteriorly in full-face view. Antennal scapes bent very close to the base, broadest at about the point of maximum curvature, with the leading edge broadly rounded and equipped with a series of projecting flattened hairs, the longest of which is about at the point of maximum scape width. Dorsum of scape just behind the leading edge with a sparse row of suborbicular hairs. Maximum diameter of eye about 0.13 X HW, less than the maximum width of the scape. Head very conspicuously dorsoventrally flattened, in profile the ventral surface not strongly convex posteriorly and the dorsum only shallowly convex at the vertex. Sides of alitrunk not marginate, the pronotum without a median longitudinal ridge or carina dorsally. Metanotal groove absent. Propodeal teeth strong, broad basally and upcurved at the tips. Dorsal alitrunk without flagellate or simple hairs of any description, only with very widely scattered extremely small inconspicuous short flattened hairs, appearing hairless under low magnification. Petiole node with a few small flattened hairs on the dorsum but fringed posteriorly and down the sides, in dorsal view, by a row of larger spatulate to squamate hairs. Lateral and posterior margins of postpetiole fringed with a similar row of spatulate to squamate hairs which project over the spongiform tissue. Dorsum of postpetiole and first gastral tergite only with minute pubescence, without hairs of any description. Spongiform appendages of pedicel segments massively developed in profile. In dorsal view the petiole node bounded posteriorly by a transverse spongiform strip which continues down the sides of the node posterolaterally, the lateral margins of the node in front of this with a few decumbent spatulate hairs but without spongiform tissue. Disc of postpetiole in dorsal view surrounded by spongiform tissue, with a transverse strip on the shallowly concave anterior margin and a broader spongiform strip on the convex posterior margin which is narrowed centrally. The spongiform material visible at the sides of the postpetiole disc is narrower and lower than the anterior and posterior strips but can be seen projecting beyond the lateral margins throughout their length. Base of first gastral tergite with a transverse spongiform strip which is overlapped by that on the posterior margin of the postpetiole and which is not narrowed centrally. Pronotal dorsum with dense but very fine low superficial longitudinal rugulae. Mesonotumsuperficially punctulate. Propodeal dorsum mostly smooth, with scattered small punctulae. Mesopleuron finely punctulate, metapleuron smooth but the sides of the propodeum with scattered quite large punctures. Petiole node faintly punctulate dorsally, the postpetiole smooth and shining. First gastral tergite unsculptured except for the short widely spaced basigastral costulae.

Type Material
Holotype worker, Ghana: Tafo, 15.x.1970, cocoa leaf litter (B. Bolton).