Messor cephalotes

Identification
A very distinctive East African species, cephalotes is one of the only two known African forms in which the gaster is strongly sculptured. The other, Messor regalis, has much coarser sculpture, as noted in the key, and also differs by having the propodeum always bidentate or bispinose, a feature only very rarely developed in cephalotes. Beside this the anterior clypeal margin, always concave in cephalotes, is shallowly convex and irregular in regalis, and the sides of the head, hairless in cephalotes, have distinct standing hairs in regalis, at least behind the eyes. (Bolton 1982)

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

Nomenclature

 *  cephalotes. Stenamma (Messor) barbarum subsp. cephalotes Emery, 1895a: 179 (w.) ETHIOPIA. Menozzi, 1939c: 102 (q.m.). Combination in Messor: Emery, 1908e: 443; in Sphaeromessor: Bernard, 1985: 48; in Messor: Bolton, 1995b: 253. Raised to species: Emery, 1908e: 443. Senior synonym of plinii: Bolton, 1982: 346.
 * plinii. Messor plinii Santschi, 1912b: 165 (s.w.) KENYA. Combination in Sphaeromessor: Bernard, 1985: 48; in Messor: Bolton, 1995b: 256. Subspecies of cephalotes: Santschi, 1917e: 94. Junior synonym of cephalotes: Bolton, 1982: 346; Bolton, 1995b: 256.

Worker
Bolton (1982) – Medium to large, HW 3.20- > 5.00.

Median portion of clypeus with anterior margin broadly but shallowly indented-concave. With the head in full-face view the occipital margin more or less transverse, very shallowly impressed medially to virtually straight, only very rarely evenly shallowly convex. Head broad and massive, very strongly transversely convex between the eyes, CI 109-123 in HW range 3.28-5.52. Eyes fairly small, their maximum diameter 0.54-0.72, about 0.13-0.17 x HW within the above-stated HW range; the relatively smaller eyes occurring in larger individuals. Psammophore generally more strongly developed in smaller than in larger workers, the characteristic hooked or J-shaped hairs sparse or absent in very large workers. Propodeal dorsum varying from rounding bluntly and evenly into the declivity to meeting the declivity in a sharp right-angle. In either case a low reinforcing lip or flange may be present which follows the curve, but prominent blunt teeth or lamellae are only very rarely known to develop. Dorsum of head blanketed everywhere with extremely fine, very densely and tightly packed, parallel longitudinal costulae; the head with a silky appearance under low magnification. The direction of the costulae is variable but usually they run straight back from clypeus to occiput centrally on the dorsum, and tend to diverge towards the occipital corners away from this central strip. In very large workers there is a tendency for the direction of the sculpture to be less regular, and even loops or whorls may occur. Dorsal alitrunk densely rugulose everywhere, the sculpture usually transverse but sometimes irregular on the propodeum. Sculpture on propodeal dorsum generally coarser and more widely spaced than on pronotum, and always coarser on pronotum than on dorsum of head. Petiole and postpetiole finely and densely sculptured with feeble rugulae, dense puncturation, or a combination of both. Base of first gastral tergite extensively sculptured with exceedingly fine close-packed scratch-like costulae, or sometimes with dense granular puncturation, or with a combination of both. The extent of this sculpture is variable but always at least the basal third of the first tergite is covered. Pilosity quite dense, all dorsal surfaces of head and body with standing hairs. With the head in full-face view the sides in front of and behind the eyes, and the curved side portions of the occipital corners, without projecting hairs; the occipital margin itself usually with conspicuous projecting hairs. Colour red to reddish dark brown, often with the gaster somewhat darker than the head and alitrunk.