Melissotarsus weissi

These ants live in galleries under the bark of trees (as do all known members of this genus). They do not forage on the surface of trees, but tend small coccids within their galleries. Nests are large with many hundreds of workers and are probably polygynous (with multiple queens) (Delage-Darchen, 1972).

Identification
Lighter coloured workers may sometimes be difficult to separate from Melissotarsus emeryi, but in general the sharper marginations of the sides of the mesosoma in weissi are fairly distinct. The sexual forms of weissi are both easily separated from those of emeryi as the male of the former is dark brown to black (pale yellow and feebly sclerotized in the latter), and the female of weissi has the postpetiole relatively narrow in dorsal view with an arched-convex anterior margin, as opposed to a very broad and distinctly transverse postpetiole in emeryi. (Bolton 1982)

Distribution based on Regional Taxon Lists
Afrotropical Region: Central African Republic, Congo, Democratic Republic of Congo, Ghana, Ivory Coast, Kenya.

Biology
Garcia, Wiesel and Fischer (2013) - The four species of this Afrotropical and Malagasy genus are rarely encountered. The Afrotropical species were revised by Bolton (1982) who also provided a good species identification key. These ants are special in several ways. They build their nests in healthy wood by tunnelling through the living tissue beneath the surface (Bolton, 1982; Fisher & Robertson, 1999; Belshaw & Bolton, 1994) and are rarely found outside of their nests, which could be the main reason for their relative scarcity in museum collections (Bolton, 1982). They live in close association with symbiotic coccids that are kept inside the nest. Adults are able to produce silk, which is used to close exit holes or to seal cracks (Fisher & Robertson, 1999).

Bolton (1982) - This small genus, of which only four uncommon species are presently recognized, is restricted to the Malagasy region (1 species) where it is rare, and the Afrotropical region (3 species) where it is, however, very widespread. The species nest in the healthy wood of living trees, apparently tunnelling their own galleries below the surface. For this reason most collections of Melissotarsus are made more by luck than by intent as their presence in the wood is usually not detectable on the surface. Delage-Darchen (1972) has shown that the method of walking in these ants is very strange; they progress on their front and hind legs with the middle pair projecting upwards, and presumably in contact with the gallery roof. She also noted the presence of coccids inside the galleries, also discussed by Ben-Dov (1978). It seems probable that coccid secretions form a major, if not the main, item in the diet of Melissotarsus species.

Nomenclature

 *  weissi. Melissotarsus weissi Santschi, 1910c: 356, fig. 3 (q.) CONGO. Bolton, 1982: 335 (m.). Senior synonym of major: Bolton, 1982: 337; of titubans: Bolton, 1995b: 250.
 * major. Melissotarsus major Santschi, 1919h: 85 (w.) DEMOCRATIC REPUBLIC OF CONGO. Santschi, 1923e: 277 (q.m.). Junior synonym of weissi: Bolton, 1982: 337.
 * titubans. Melissotarsus titubans Delage-Darchen, 1972a: 216, figs. 1-10 (w.q.m.) IVORY COAST. Wheeler, G.C. & Wheeler, J. 1980: 531 (l.). Junior synonym of beccarii: Bolton, 1982: 336; of weissi: Bolton, 1995b: 250 (syntypes examined).

Bolton (1982) - So little material of Melissotarsus is available at present that this survey must be regarded as strictly preliminary. Three species are now recognized in the Afrotropical region but it is possible that each may be compounded of more than one different sibling-species. Conversely it is by no means impossible that further collections will bridge what appear here as species for the differences between them, though consistent in the few samples to hand, are relatively minor and may well be anulled by further collecting.

The three presently recognised species are basically so similar that to present a full description for each would be redundant so, for the purposes of identification, a description of the type-species beccarii is given and the other two are compared to it.

The shape of the mesosoma in dorsal view shows subtle but perhaps significant differences between separate series of workers presently grouped as single species, but discovering whether these differences are meaningful, or even consistent, will have to await the amassing of considerably more samples than are presently available.

For the present I define weissi as having a dark brown to black strongly sclerotized male, and a similarly coloured female in which the postpetiole in dorsal view is quite narrow (1.20-1.40 x broader than long) and has a rounded or even hemispherical anterior margin. The worker of weissi has the mesosoma medium to dark reddish brown, the anterior margin of the pronotum in dorsal view sharply defined and angular where it meets the anterior declivity, and the sides of the mesosoma meeting the dorsum in a fairly well-defined angle.

Worker
Bolton (1982) - TL 2.3-3.0, HL 0.58-0.74, HW 0.60-0.78, CI 98-104, SL 0.27-0.34, SI 41-47, PW 0.36-0.50, AL 0.56-0.84 (14 measured).

Answering to the description of Melissotarsus beccarii but darker in colour, the mesosoma medium to dark reddish brown; with the anterior pronotal margin meeting the anterior declivity in a well-defined angle or edge, and with the sides of the mesosoma meeting the dorsum in a fairly well-marked angle.