Sphinctomyrmex

Species of Sphinctomyrmex are specialist predators of other ants. They primarily forage below ground, only rarely on the surface. Most species lack fully winged queens and have, instead, worker-like (ergatoid) queens. Workers have a relatively heavy integument with angles and teeth for protection during raids. Nests are in soil, in downed wood and under stones. They may contain several hundred workers and up to 20 or more ergatoid queens. Some species from Australia seem to be comparatively army-ant like and have more or less dichthadiiform queens; these species perform mass raids on other ants and are presumably nomadic (Brown, 1975; Buschinger et al., 1990).

Identification
Sphinctomyrmex can be separated from Cerapachys by the shape of the gaster. Its shape is unique to Sphinctomyrmex and should allow ready identification of members of this genus.

Distribution
Sphinctomyrmex occurs in the tropics of the New and Old World. Most species occur in Australia (Brown, 1975; Bolton, 2012).

Species richness
Species richness by country based on regional taxon lists (countries with darker colours are more species-rich). View Data



Biology
Brown (1975) - Most species of Cerapachys and Sphinctomyrmex appear to nest in the ground or in rotten wood. Nests I have seen in moist forested areas usually have one or a few relatively capacious chambers connected to the surface by a short passage, but in arid areas, there may be several chambers 10-50 cm or more deep in the soil, with longer tunnels. Sometimes the nest is under a rock. The entrance is usually an inconspicuous hole without a crater, but in a few cases, a small crater or turret occurs at the surface.

Nest populations can contain as few as 20 adult workers to more than a thousand; the higher counts hold for some species of Sphinctomyrmex and the Cerapachys typhlus and antennatus groups, but most Cerapachys nests probably contain less than 200 workers. Pupae are normally enclosed in cocoons. The winged males are very active when mature and may attempt to take flight when the nest is opened.

The more advanced and probably more army-ant-like species of Sphinctomyrmex (imbecilis, froggatti, perstictus, trux, mjobergi, etc.) apparently have a single, more or less dichthadiiform queen, although the picture is confused by the appearance in some of these species of additional “ergatoid” forms that could just possibly have some reproductive function. It is such species that probably have the males with falcate mandibles.

In other species with dealate or less completely modified reproductives (e.g., steinheili, duchaussoyi, asper, occidentalis) each nest may contain several, up to 20 or more, of these ergatoid queens. Of course, we do not know how many such individuals in a given nest may function as true reproductives, or to what extent, if they do so function.

Nomenclature

 *  SPHINCTOMYRMEX [Cerapachyinae: Cerapachyini]
 * Sphinctomyrmex Mayr, 1866b: 895. Type-species: Sphinctomyrmex stali, by monotypy.
 * Sphinctomyrmex senior synonym of Aethiopopone: Bolton, 1973a: 341; Brown, 1975: 31.
 * Sphinctomyrmex senior synonym of Eusphinctus, Nothosphinctus, Zasphinctus: Brown, 1975: 31.
 * AETHIOPOPONE [junior synonym of Sphinctomyrmex]
 * Aethiopopone Santschi, 1930a: 49. Type-species: Sphinctomyrmex rufiventris, by monotypy.
 * Aethiopopone junior synonym of Sphinctomyrmex: Bolton, 1973a: 341; Brown, 1975: 31.
 * EUSPHINCTUS [junior synonym of Sphinctomyrmex]
 * Eusphinctus Emery, 1893a: cclxxv. Type-species: Eusphinctus furcatus, by monotypy.
 * Eusphinctus subgenus of Sphinctomyrmex: Emery, 1895k: 456.
 * Eusphinctus revived status as genus: Wheeler, W.M. 1918a: 219.
 * Eusphinctus junior synonym of Sphinctomyrmex: Brown, 1975: 31.
 * NOTHOSPHINCTUS [junior synonym of Sphinctomyrmex]
 * Nothosphinctus Wheeler, W.M. 1918a: 219 [as subgenus of Eusphinctus]. Type-species: Sphinctomyrmex froggatti, by subsequent designation of Donisthorpe, 1943f: 675.
 * Nothosphinctus junior synonym of Sphinctomyrmex: Brown, 1975: 31.
 * ZASPHINCTUS [junior synonym of Sphinctomyrmex]
 * Zasphinctus Wheeler, W.M. 1918a: 219 [as subgenus of Eusphinctus]. Type-species: Sphinctomyrmex turneri, by monotypy.
 * Zasphinctus junior synonym of Sphinctomyrmex: Brown, 1975: 31.

Brown (1975):

Worker
With characters of Cerapachys, but gastric segments IV, V, and VI separated by distinct constrictions and (except for Sphinctomyrmex furcatus and Sphinctomyrmex taylori) nearly equal in length. Eyes reduced to very small size or altogether lacking (except in S. turneri, which has fairly large, convex eyes). Antennae with 11 or 12 segments; palpi usually segmented 3,3. Sculpture of round piligerous foveolae, sparse or crowded, with smooth or finely roughened interspaces. Hairs short, simple, sparse to fairly dense; pubescence sometimes present on petiole, postpetiole, or succeeding gastric segments. Color black, brown, red, or yellow.

Queen
A morphocline ranges from perfect winged (or dealate) females with large eyes, ocelli, etc., to blind subdichthadiiform queens that are workerlike except for larger size and broader head and petiole, and sometimes vestigial eyes and 1 ocellus. Intermediates exist in, e.g., Sphinctomyrmex steinheili and Sphinctomyrmex asper; these may have compound eyes of modest size and 3 ocelli, but workerlike trunk. It seems likely that the species with subdichthadiiform queens have monogynous colonies, while at least some of the dealate or intermediate forms are found several (to more than 20) to a single colony. Dissections in Sphinctomyrmex steinheili indicated that the multiple queens are all functional reproductives (Buschinger et al. 1989).

Male
Differs from Cerapachys male by the distinctly constricted subequal segments of the gaster, and even here a difficulty exists because some American Cerapachys have narrowed bases to the main gastric segments. The male of Sphinctomyrmex furcatus, like its worker, has the gastric segments unequal, with the first much the largest. Antennal segments 13, rarely (S. furcatus) 12.

Aside from Sphinctomyrmex furcatus, males of Sphinctomyrmex divide into 2 classes. The first class, associated in a few cases with workers and / or queens (Sphinctomyrmex steinheili, Sphinctomyrmex turneri, Sphinctomyrmex asper) has slender males with triangular mandibles, and usually distinct notauli. The second class, consisting of males taken at light, probably belongs with the species having subdichthadiiform queens (froggatti group); these have long, tapered, falcate mandibles and lack distinct notauli; they tend to be larger and relatively robust, and have denser, softer, more regularly arranged pilosity, particularly on head and mandibles.