Calyptomyrmex

Members of the genus Calyptomyrmex are rare ants that forage on the ground or in leaf litter. They are most commonly encountered in rainforests where they forage singly or in small numbers (Bolton, 1981). The few nests that have been found were in rotten wood (Shattuck, 1999; Taylor, 1991) or directly in soil (Bolton, 1981). Workers are often covered with a layer of soil, the enlarged and often spatulate hairs presumably assisting in the retention of this camouflaging material. Similar behaviours are known in many species of basicerotines as well as Stegomyrmex (Holldobler & Wilson, 1986), this behaviour being convergent as these groups are not closely related. The majority of species of Calyptomyrmex are known from only limited numbers of collections, with even the most common having been collected fewer than 20 times. Although this rarity makes estimates of true distribution patterns problematic, it appears that most species have restricted ranges while only a single species has become widespread.

Biogeographically, Calyptomyrmex is known from Africa and India east to New Caledonia. Baroni Urbani (1975) revised the fauna of the Indian subcontinent and Bolton (1981) the Afrotropical species while Shattuck (2011) investigated the fauna of South-east Asia and eastward. Shattuck (2011) added 14 new species, bringing the total known for the genus to 28 (Bolton et al., 2006). Taylor (1991) provided an overview of the Australian fauna, synonymised the only Australian-based name with the widespread species Calyptomyrmex beccarii and outlined seven undescribed Australian species (although none were formally named).

The South-east Asian Calyptomyrmex fauna is similar in diversity to that of Australia, with eight species so far known (Calyptomyrmex asper, Calyptomyrmex beccarii, Calyptomyrmex danum, Calyptomyrmex loweryi, Calyptomyrmex rectopilosus, Calyptomyrmex retrostriatus, Calyptomyrmex ryderae, Calyptomyrmex sabahensis), one of these (Calyptomyrmex beccarii) being shared with Australia. Given that many of these species are known from only single or a few collections it is likely that additional species exist which are yet to be encountered. Only single species are known from Papua New Guinea (Calyptomyrmex beccarii) and New Caledonia (Calyptomyrmex caledonicus).

Identification
Workers belonging to Calyptomyrmex may be separated from those of other myrmicine genera by the presence of distinct, elongate depressions (antennal scrobes) on the front of the head which contain the entire antennae when at rest and the conspicuous, broad, bilobed appendage (the clypeal fork) which projects over the rear section of the mandibles. The deep antennal scrobes and the unique configuration of the clypeus will separate these ants from all others. For a more complete description see Bolton (1981).

Eguchi, Bui and Yamane (2011) - The worker of the Vietnamese species is somewhat similar to that of Mayriella, but in the latter the antenna is 10-segmented, the eye is large and elongate, and the dorsa of the head and mesosoma bear sparse, long, standing hairs.

Nomenclature

 *  CALYPTOMYRMEX [Myrmicinae: Stenammini]
 * Calyptomyrmex Emery, 1887b: 471. Type-species: Calyptomyrmex beccarii, by monotypy.
 * Calyptomyrmex senior synonym of Weberidris: Donisthorpe, 1949f: 186; Brown, 1949f: 84.
 * WEBERIDRIS [junior synonym of Calyptomyrmex]
 * Weberidris Donisthorpe, 1949a: 281. Type-species: Weberidris rufobrunnea (junior synonym of Calyptomyrmex beccarii), by original designation.
 * Weberidris junior synonym of Calyptomyrmex: Donisthorpe, 1949f: 186; Brown, 1949f: 84.