Monomorium invidium

Known from a variety of forest habitats, it has commonly been found in litter sampling.

Identification
Bolton (1987) - M. invidium is the commonest and most widely distributed member of this small group in West Africa: It separates easily from the other two known West African species as Monomorium jacksoni, known only from Cameroun, is much more strongly sculptured, and Monomorium guineense from Guinea has much narrower scale-like nodes.

The non-paratypic material shows the following range of dimensions. TL 1.8-2.3, HL 0.46-0.56, HW 0.39-0.48, CI 82-86, SL 0.32-0.38, SI 79-84, PW 0.30-0.34, AL 0.50-0.62 (15 measured). In these series eye size shows the range 0.14-0.17 x HW and the eyes have 3-5 ommatidia in the longest row. In larger workers the peripheral ring of ommatidia may surround 5 others, rather than the 2-3 which seems more usual. In some individuals the sculpture of the propodeal dorsum is almost or entirely effaced, leaving the surface glassy smooth. Similarly the sides of the alitrunk may lack sculpture except in the vicinity of the metapleural gland bulla. Outline shape of the propodeum in profile varies from narrowly but bluntly rounded to sharply obtusely angular.

Distribution based on Regional Taxon Lists
Afrotropical Region: Cameroun, Ghana, Guinea, Ivory Coast, Nigeria, Uganda.

Nomenclature

 *  invidium. Monomorium invidium Bolton, 1987: 427, figs. 97, 98 (w.q.) NIGERIA.

Worker
Holotype. TL 1.9, HL 0.48, HW 0.41, CI 85, SL 0.34, SI 83, PW 0.31, AL 0.54.

Mandibles smooth and shining, unsculptured except for scattered hair-pits. Pair of teeth on anterior clypeal margin conspicuous. Maximum diameter of eye 0.15 x HW, with 4 ommatidia in the longest row; the outer peripheral ring of ommatidia enclosing only two ommatidia within the ring. Promesonotum shallowly convex in profile, the metanotal groove narrow and shallowly impressed. Propodeal dorsum sloping downwards posteriorly and rounding narrowly into the declivity, the dorsal surface of the propodeum bluntly marginate laterally and the dorsum between the blunt margins very shallowly concave. Petiole and postpetiole in profile high and narrow, the nodes narrowly but bluntly rounded above and the latter node slightly thicker than the former. In dorsal view the nodes broadly transversely elliptical. Cephalic dorsum behind the frontal lobes smooth, unsculptured except for hair-pits. Sides of head without a narrow sculptured strip running from the anterior margin of the eye to the base of the mandible, and the occipital margin unsculptured. Promesonotum smooth and highly polished both dorsally and laterally. Remainder of sides of alitrunk with sculpture only on lower half and round the margin of the mesopleuron, on the metapleuron, and with a small sculptured patch on the propodeum behind the level of the spiracle. Propodeum in dorsal view finely and faintly transversely rugulose. Petiole postpetiole and gaster unsculptured in dorsal view. All dorsal surfaces of head and body with numerous standing hairs. Colour highly polished blackish brown.

Paratypes. TL 1.8-2.0, HL 0.48-0.50, HW 0.40-0.42, CI 82-85, SL 0.33-0.36, SI 81-86, PW 0.30-0.31, AL 0.54-0.56 (10 measured). As holotype but eyes may have 3-4 ommatidia in the longest rowand have maximum diameter 0.15-0.17 x HW. Sculpture on propodeal dorsum is sometimes effaced medially, being visible only close to and on the lateral marginations. On the sides of the alitrunk the mesopleuron may be smooth with only peripheral sculpture developed, and the sculptured patch behind the propodeal spiracle is sometimes absent. Colour varies from blackish brown to jet black.

Type Material
Holotype worker, Nigeria: Ibadan, UTA, sample 06, 28.iv. 1981 (A . Russell-Smith). Paratypes. 10 workers and one dealate female with same data as holotype (BMNH; ; ).