Melissotarsus beccarii

Nothing is known about the biology of .

Identification
The key character given to separate beccarii and Melissotarsus emeryi workers is quite weak. In most individuals there is a reasonable visible difference between the two, with the anterior pronotal margin rounding bluntly into the declivity in beccarii, and with the anterior pronotal margin separated from the declivity by an angle or edge in emeryi. Having said that, however, it should be pointed out that the difference is not so well marked in some individuals, which in consequence are difficult to place. Both species have a pale yellow feebly sclerotized male. Females of both species have the postpetiole in dorsal view conspicuously broader than long but it seems that two species are present as in some the mesoscutum is longer than broad (beccarii) but in others broader than long (emeryi). It should be admitted that very few worker-associated females are known and further collections may annul this apparent difference. To sum up, for the present I recognise these two as separate on the strength of the differently shaped mesoscutum in females and the form of the anterior pronotal margin in workers, but harbour a suspicion that only a single real species may in fact be represented here. M. beccarii differs from Melissotarsus weissi fairly consistently in all castes. The workers of weissi are darker in colour than those of beccarii and have both the anterior pronotal margin and the sides of the alitrunk relatively strongly marginate. The male is dark brown to black and strongly sclerotized, and in the female the postpetiole is relatively narrow in dorsal view with an arched-convex anterior margin which is quite different in shape from the strongly transverse form seen in beccarii. (Bolton 1982)

1)

-With the alitrunk in dorsal view the anterior margin of the pronotum rounding evenly into the anterior declivity, the two not meeting in a sharp angle or edge. (Ethiopia, Tanzania, South Africa, Ivory Coast). . . . . beccarii

-With the alitrunk in dorsal view the anterior margin ofthe pronotum separated from the anterior declivity by a sharp angle or edge. . . . . 2

2)

-Sides of alitrunk meeting dorsum in a fairly well-defined angle. Alitrunk colour medium to dark reddish brown. (Ghana, Congo, Zaire). . . . . weiss

-Sides of alitrunk rounding bluntly into the dorsum. Alitrunk colour yellow to light yellowish brown. (Ethiopia, Sudan, Kenya, Tanzania, Zaire, Central African Republic. South Africa, Ivory Coast, Ghana). . . . . emeryi

Distribution based on Regional Taxon Lists
Afrotropical Region: Eritrea, Ivory Coast, South Africa, Tanzania. Palaearctic Region: Ethiopia.

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

 *  beccarii. Melissotarsus beccarii Emery, 1877b: 379, fig. (w.) ETHIOPIA. Forel, 1914d: 243 (q.m.). See also: Arnold, 1916: 189; Bolton, 1982: 336.

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 alitrunk 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.

M. emeryi and beccarii have pale yellow feebly sclerotized males, and have females in which the postpetiole in dorsal view is quite broad (1.90-2.20 x broader than long) and lacking a rounded anterior margin, the margin instead being more or less straight or even slightly concave. The workers are yellow to light yellowish brown and have the sides of the alitrunk rounding bluntly into the dorsum when seen in dorsal view. Females of emeryi differ from those of beccarii as in the former the mesoscutum is broader than long in dorsal view; it is longer than broad in the latter. Workers of emeryi have the anterior margin of the pronotum sharply defined and angular where it meets the anterior declivity, whereas in beccarii there is no such sharp differentiation between dorsum and anterior declivity, instead the one surface rounds bluntly into the other.

Worker
Bolton (1982) - TL 2.3-3.3, HL 0.56-0.82, HW 0.56-0.80, CI 97-105, SL 0.24-0.34, SI 39-47, PW 0.34-0.55, AL 0.58-0.80 (15 measured).

With the head in full-face view the occipital margin concave, sometimes deeply so medially, and with the sides convex and weakly to distinctly convergent in front of the eyes. Mandibles with a long finger-like apical tooth, worn down to nothing in some specimens; the mandibles unsculptured. Eyes much longer than broad, strip-like in many, the maximum diameter 0.12-0.16, about 0.18-0.22 x HW. Median portion of clypeus raised above the level of the lateral portions, not extending back between the frontal lobes; the latter contiguous and separated only by an impressed line. Scapes very short, SI < 50. Alitrunk in dorsal view with anterior pronotal margin rounding into the declivity, the two surfaces not separated by a sharp edge or angle. Dorsum of alitrunk roughly rectangular longitudinally, somewhat narrower behind than in front but not strongly so, and with the dorsum rounding into the sides. In profile the promesonotal dorsum and anterior propodeum are more or less fiat but the posterior part of the propodeum rounds very broadly and evenly into the declivity, without trace of armament. Fore coxae small, about half the size of the strongly swollen middle and hind coxae. Peduncle of petiole short and grading into the relatively high narrow node, the node with a short posterior free face, broadly attached to the postpetiole. In dorsal view the petiole node much broader than long. Postpetiole in dorsal view much broader than long, slightly broader than the petiole and very broadly attached to the first gastral tergite without a posterior constriction. Gaster only feebly sclerotized, crumpled in most mounted specimens. Dorsum of head with a silky superficial ground-sculpture upon which scattered small pits are usually superimposed. The ground-sculpture may cover the whole head but frequently it fades out occipitally. Median portion of clypeus more densely and strongly sculptured than dorsum of head capsule. Dorsal alitrunk finely longitudinally costulate throughout, the costulae fading out where the propodeal dorsum rounds into the declivity. Dorsal surfaces of head, scapes, pronotum, mesonotum, pedicel segments and gastral tergites with scattered sparse long fine hairs. Propodeal dorsum usually with one or two shorter hairs but these are frequently missing. Dorsal (outer) surfaces of tibiae with sparse long hairs similar to those on alitrunk. Head and alitrunk dull yellowish brown to dark yellow, the gaster lighter, usually pale dull yellow.