Myrmoteras species groups

Moffett (1985) partitioned what was, at the time of his publication, the known species into subgenera and species groups. Many new species have been described since then, and the genus has more than doubled in the number of species. Authors describing new species after 1985 have mostly ignored assigning species to these subgenera and groups.

There is a key to all the species Moffett treated in his revisions of the genus: Key to Myrmoteras.

Subgenus Myrmoteras
Workers and queens readily distinguished from subgenus Myagroteras by the presence of a pair of prominent trigger hairs. When viewed in perfect full face, the visible part of the labrum is triangular, coming to a more or less distinct forward point from which the trigger hairs originate. Although initially directed somewhat downward and between the bases of the mandibles, the hairs curve gently forward and then extend directly ahead immediately beneath the mandible shafts to 45 to 95% of the distance to the apical tooth. The hairs are much thicker than other body hairs, and are pliable, rarely breaking even in dried material. In some museum specimens the hairs are bent and widely separated. In life, however, the hairs are aligned very close together, if not in actual contact through their lengths.

Frontal sulcus very feeble or absent, usually visible only as a slight trace of an impressed line in some lights; never conspicuous as in Myagroteras. Orbital grooves moderately developed to virtually absent; never conspicuous. Narrow ridges curving above antennal carinae absent or moderately developed. Frontal area usually not demarcated at all. Clypeus feebly convex over a broad median region or (in M. brachygnathum and ceylonicum) more strongly convex; but with lateral flanges somewhat less conspicuous than in Myagroteras because shift in plane relative to margins of the raised medial region is reduced.

Mandibles shorter than in most Myagroteras species, as long as trunk or shorter (ML/WL < 0.95 except in some M. iriodum workers). The mandible shafts bend ventrad about 45° at about the position of the penultimate tooth (less strongly bent in ceylonicum). In dorsal view outer margins of shafts proximately virtually straight to feebly convex (becoming progressively more strongly convex distad); without a slight bend at about a third the distance to the mandible tips. Apical denticles often larger and stouter than in Myagroteras.

This subgenus contains seven species distributed from India and Sri Lanka to Thailand, peninsular Malaysia, Borneo and Java. Included are all of the largest species of Myrmoteras (species with head widths of 1.10 mm or more); however, two species in the ceylonicum group are relatively small. The worker is known for all species, the queen for three, and the male for none.

binghami group
Size medium to large (TL 5.5 to 7.0 mm). Head narrower than in ceylonicum group (CI < 102); occipital lobe slightly thicker (OLI 10 to 13). Orbital grooves essentially absent, but the apparent remnants usually visible as extremely narrow, feebly impressed grooves dorsad along margins of eyes. Frontal area not demarcated (except in Myrmoteras binghami, in which the frontal area is visible but ill defined). Ridges above antennal bases essentially absent. Palpal segmentation variable; known extremes 6,4 and 4,3. Mandibles longer than in ceylonicum group (MI > 110); number of mandible teeth usually 11 to 13 (8 to 9 in binghami). Apical denticles often large, sometimes pair reduced to a single denticle. Mandibles bent ventrad distally to a degree intermediate between that described for Myrmoteras ceylonicum and Myrmoteras scabrum in the ceylonicum group; that is, when viewed from above with the basal portion of the shafts perpendicular to the angle of view, the apical tooth and subapical denticles are obviously shifted out of the plane of the other teeth, but not so strongly as to be obscured by the penultimate tooth. Integument lustrous, but in addition head and trunk with a feeble to moderately conspicuous iridescent sheen (virtually lacking on mesothorax) not found in any other species in the genus.

Species in this group are known from Thailand and the Malay Archipelago. What little information is available indicates these ants inhabit moist tropical forests.

ceylonicum group
Small to medium species (worker 3.9 to 5.5 mm TL). Head broad (CI > 108); occipital lobe slightly less massive than in binghami group (OLI 5 to 8). Orbital grooves moderately developed, more conspicuous than in the binghami species group. Frontal area present but poorly demarcated (absent in Myrmoteras brachygnathum). Ridges above antennal bases moderately developed. Palpal segmentation variable; known extremes 6,4 and 3,3 (4,2 in Myrmoteras scabrum?). Mandibles conspicuously shorter than in any other species, no longer than head (MI less than 102). Number of mandibular teeth eight to nine; apical denticles both present, but small. Head and trunk lustrous, completely lacking the feeble iridescent sheen typical of the binghami group.

This distinctive group includes three species from southern India and Sri Lanka, all of which have been collected in areas of evergreen forest at moderate to high elevations (600 to 2,200 m).

Subgenus Myagroteras
See the Myagroteras subgenus page.