Tetramorium browni

An arboreal species that is known from tree fogging samples in rainforest and other forest habitats.

Identification
Bolton (1980) - Of the four yellowish (as opposed to uniform dark brown) species of the T. camerunense-complex one, Tetramorium luteipes, has finely striate mandibles. The remaining three, Tetramorium gegaimi, T. browni and Tetramorium miserabile, have smooth or virtually smooth mandibular blades. In T. gegaimi the petiole in dorsal view has the anterior face bordered by a narrow ridge or crest which separates dorsum from anterior face; this feature is absent in T. browni and T. miserabile, where all faces of the node round into the dorsum. Also, in T. gegaimi pronotal sculpture is a rugoreticulum, as opposed to the longitudinal organization seen in the other two. In T. browni the hairs on the dorsal alitrunk are elongate, acute apically and fine, the longest of these hairs distinctly longer than the maximum diameter of the eye. In contrast the alitrunk pilosity of T. miserabile is short, stout and blunt, all the hairs being markedly shorter than the eye diameter.

Included as non-paratypic material are five other samples each from a different locality and each represented by only a single individual. In most of these the pronotal sculpture is by no means as regular as in the holotype, but in each case it is noticeably more regular and more widely (and usually more evenly) spaced than the rugulae occurring more posteriorly on the alitrunk.

Distribution based on Regional Taxon Lists
Afrotropical Region: Ghana.

Nomenclature

 *  browni. Tetramorium browni Bolton, 1980: 337 (w.) GHANA.

Worker
Holotype. TL 2.8, HL 0.69, HW 0.63, CI 91, SL 0.45, SI 71, PW 0.40, AL 0.74. Paratypes (6 measured): TL 2.6-2.9, HL 0.64-0.70, HW 0.58-0.66, CI 90-94, SL 0.42-0.48, SI 71-75, PW 0.38-0.43, AL 0.72-0.82. Maximum diameter of eye 0.12-0.14, about 0.21-0.23 x HW.

Mandibles smooth and shining with scattered pits. Anterior clypeal margin with a small median notch. Median clypeal carina sharp and distinct, flanked by a pair of weaker carinae, otherwise clypeus unsculptured. Frontal carinae narrow and very fine, extending back almost or quite to the occipital margin without becoming confused with the other cephalic sculpture. Eyes moderate, maximum diameter 0.14, about 0.22 x HW and with 9 ommatidia in the longest row. Dorsum of alitrunk evenly shallowly convex in profile. Propodeal spines acute, more or less straight, rapidly tapering from base to acute apex and distinctly longer than the triangular, slightly upcurved metapleural lobes. Node of petiole in profile higher than long, with both antero- and posterodorsal angles bluntly but narrowly rounded. In dorsal view the petiole node slightly broader than long, rounded, the dorsum curved into the sides and the anterior and posterior faces, without a low rim or crest separating dorsum from sides or anterior face. Dorsum of head quite regularly, very finely longitudinally rugulose; the rugulae quite sharply defined though narrow, and with 11-12 between the frontal carinae at eye level. Ground-sculpture minimal on the dorsum, merely a very faint superficial pattern, the surfaces glossy. Sides of head between eye and frontal carina with a more conspicuous punctulate ground-sculpture traversed by a few faint rugulae. Occipital area without a rugoreticulum. Pronotum with a sharp transverse crest separating dorsum from anterior declivity, the anterior portion of the dorsum behind the crest with regularly spaced sharp longitudinal rugulae. On the posterior portion of the pronotum, the mesonotum and the propodeum the rugulae becoming progressively fainter and more disorganized, with some cross-meshes and anastomoses. Ground-sculpture virtually absent on pronotum but becoming stronger posteriorly where it forms a weak, superficial punctulation only; all surfaces glossy. Petiole, postpetiole and gaster unsculptured. All dorsal surfaces of head and body with numerous fine standing hairs which are acute apically; the longest of those on the alitrunk distinctly longer than the maximum diameter of the eye. Tibiae of middle and hind legs only with minute decumbent to appressed pubescence. Colour glossy dull yellow, the gaster brown.

Paratypes: Dorsum of head with 11-13 rugulae between frontal carinae at eye level; the eye with 8-9 ommatidia in the longest row. In some the rugulae on the anterior pronotum are not nearly as regularly organized as in the holotype.

Type Material
Holotype worker, Ghana: Tafo, 21.x.1970, rotten log (B. Bolton). Paratypes. 6 workers with same data as holotype (BMNH; ; ).

References based on Global Ant Biodiversity Informatics

 * Bolton B. 1980. The ant tribe Tetramoriini (Hymenoptera: Formicidae). The genus Tetramorium Mayr in the Ethiopian zoogeographical region. Bulletin of the British Museum (Natural History). Entomology 40: 193-384.