Strumigenys rukha

A relatively well collected species that occurs in a range of forest habitats. Specimens have been found in litter, downed wood, under stones and soil.

Identification
Bolton (2000) - A member of the Strumigenys scotti-group. Mandibles with outer margins evenly bowed outwards along their length (averaging shorter than in Strumigenys adrasora where MI is 50-54). Distal preapical tooth on left mandible about three-quarters length of proximal. Scape somewhat thickened distal of basal third, beyond thickened portion tapering to apex. Hairs on leading edge of scape and fringing upper scrobe margin spatulate, the latter somewhat longer and thicker than the former. Preocular notch minute to absent. Lamella on propodeal declivity broad and conspicuous. Ventral spongiform strip present on petiole. Ventral spongiform lobe of postpetiole in profile larger than exposed area of disc.

Bolton (1983) - S. rukha is most closely related to Strumigenys adrasora, Strumigenys relahyla, and Strumigenys dyshaula. It is easily separated from the first of these as in adrasora the spongiform appendages of the pedicel segments are small, the ventral postpetiolar lobe being smaller than the exposed portion of the postpetiolar disc in profile. In rukha the spongiform appendages are better developed than in dyshaula and relahyla, but in dyshaula the distal preapical tooth of the left mandible is much more slender than the proximal and only about half of its length, whereas in rukha the distal pre apical tooth of the left mandible is only marginally narrower than the proximal and is three-quarters or more of its length. In relahyla the mandibles are slightly shorter (MI 43-46) and stouter than in rukha (MI 47-49) and the preocular notch is much more strongly impressed.

Distribution based on Regional Taxon Lists
Afrotropical Region: Kenya, Uganda.

Nomenclature

 *  rukha. Strumigenys rukha Bolton, 1983: 389 (w.q.) KENYA. See also: Bolton, 2000: 610.

Worker
Holotype. TL 2.4, HL 0.60, HW 0.45, CI 75, ML 0.28, MI 47, SL 0.33, SI 73, PW 0.29, AL 0.58.

Mandibular blades with their outer margins shallowly convex, feebly bowed outwards in full-face view. Mandibular apices each with a fork of 2 teeth, without intercalary teeth or denticles. Each blade with preapical armament of2 teeth, the proximal the longest. Distal pre apical tooth of left mandible longer than the distance separating its base from that of the proximal pre apical tooth. Upper scrobe margins evenly divergent posteriorly, the eyes visible in full-face view. Maximum diameter of eye about equal to or very slightly greater than the maximum width of the scape, the eye with 14--15 ommatidia. Preocular notch present but vestigial, represented only by an inconspicuous shallow indentation of the ventrolateral margin immediately in front of the eyes; the preocular notch not continued onto the ventral surface of the head as a transverse groove or impression. Antennal scapes very shallowly curved in the basal third, the median third expanded to about twice the basal width. Leading edges of scapes equipped with an apically curved row of slender spatulate hairs which are smaller than the projecting hairs fringing the upper scrobe margins. Ground-pilosity of cephalic dorsum of inconspicuous short flattened to spatulate curved hairs, the upper scrobe margins fringed by an anteriorly curved row of much larger hairs which are spatulate to narrowly spoon-shaped. Dorsum of head with 6 standing hairs arranged in a transverse row of 4 close to the occipital margin and a more anteriorly situated pair. Cephalic dorsum reticulate-punctate. Pronotal humeri each with a fine flagellate hair. Mesonotum with a single pair of stout standing hairs. Ground-pilosity of dorsal alitrunk of sparse inconspicuous hairs similar to those on the head. Posterior portion of mesonotum depressed behind the level of the pair of hairs. Metanotal groove represented by a feebly marked line across the dorsum, not impressed. Propodeal teeth short and broadly triangular, subtended by a broad infradental lamella on each side which is confluent with the tooth for half or more of its length. Sides of alitrunk mostly smooth, the pronotal sides with vestigial superficial reticulate markings and the pleurae with faint peripheral punctures. Pronotal dorsum longitudinally finely costulate-rugulose, the remainder of the dorsal alitrunk punctate. Petiole node punctate dorsally, the postpetiole smooth and shining. Spongiform appendages of pedicel segments well developed, the petiole ventrally with a broad spongiform strip which follows a basal low broad translucent triangular lobe. Ventral spongiform lobe of postpetiole larger than the lateral lobe and larger than the exposed area of the postpetiolar disc in profile. Petiole node in dorsal view transversely rectangular, with a posterior transverse lamella. Postpetiole surrounded on all sides with spongiform material, the lateral and ventral lobes projecting beyond the outline of the disc and visible in dorsal view. First gastral tergite with a narrow basal strip from which the sharply defined basigastral costulae arise. Petiole, postpetiole and gaster dorsally with standing stout hairs. Colour yellow.

Paratypes. TL 2.3-2.4, HL 0.57-0.60, HW 0.44-0.46, CI 75-79, ML 0.27-0.28, MI 47-49, SL 0.30-0.33, SI 67-73, PW 0.28-0.30, AL 0.56-0.69 (10 measured).

As holotype but in some the mesonotum with a shallow transverse impression at the base of the descending portion of the sclerite. The translucent lobe at the base of the petiole ventrally is very variable in shape and size. In most workers it is a triangular to rounded lobe but in some is much reduced and rarely it may be absent. The preocular notch, weakly developed at best, may be undetectable.

Type Material
Holotype worker, Kenya: Embu, Kirimiri Forest, W. of Runyenje, 1550 m, 3.x.1977 (V. Mahnert & J.-L. Perret). Paratypes. 42 workers and 2 females with same data as holotype (MHNG; ; ; ).

References based on Global Ant Biodiversity Informatics

 * Bolton B. 1983. The Afrotropical dacetine ants (Formicidae). Bulletin of the British Museum (Natural History). Entomology 46: 267-416.
 * Bolton, B. 2000. The Ant Tribe Dacetini. Memoirs of the American Entomological Institute 65
 * Garcia F.H., Wiesel E. and Fischer G. 2013.The Ants of Kenya (Hymenoptera: Formicidae)Faunal Overview, First Species Checklist, Bibliography, Accounts for All Genera, and Discussion on Taxonomy and Zoogeography. Journal of East African Natural History, 101(2): 127-222
 * IZIKO South Africa Museum Collection
 * Nousiainen A. 2017. Leaf litter ants in indigenous rainforest and coniferous plantations of the Taita Hills, Kenya. Master Thesis University of Helsinki, 53 pages.
 * Ross S. R. P. J., F. Hita Garcia, G. Fischer, and M. K. Peters. 2018. Selective logging intensity in an East African rain forest predicts reductions in ant diversity. Biotropica 1-11.