Cataulacus is a genus of ants in the subfamily Myrmicinae. The genus is distributed in the Paleotropical regions, mainly in the Afrotropics. Most species are found in forests, but a few are known from more open and arid habitats.
Worker. - Small or medium-sized, rather flat, opaque or subopaque, black ants, with coarse sculpture and the head and thorax often dentate or spinulate on the sides. Antennae in all three phases 11-jointed with 3-jointed club and apically flattened or dilated scape. Head on each side with a deep scrohe situated beneath and external to the eye and capable of accommodating the whole of the folded antenna. The frontal carinae are far apart, anil diverge, but border the scrobes only at the base. The clypeus Ls wedged in between the frontal carinae and is not sharply delimited posteriorly. Thoracic sutures often indistinct or obsolete. Epinotum armed with spines. Petiole and postpetiole stout, the former usually more or less cuboidal, with a laminate process below, the latter subglobular. Gaster elliptical or suboblong, flattened, the first segment forming its whole dorsal surface. Legs rather short, the femora and tibiae incrassated.
The female, though larger, closely resembles the worker. The pronotum is large and forms a considerable portion of the thoracic dorsum. Wings without a discoidal cell, with a single cubital and a narrowly open radial cell.
The male resembles the female and worker in the shape of the head but has larger and longer petiole and postpetiole. The mesonotum has well-developed Mayrian furrows.
The ants of the genus Cataulacus bear a strange superficial resemblance, both in structure and habits, to those of the Neotropical genus Cryptocerus. The genus ranges over tropical Africa and eastward over Madagascar, India, Indonesia, and the Philippines, but is represented by the greatest number of species in the Ethiopian Region (Map 30). Concerning the habits, Arnold says that "all the species of this genus are tree-ants, usually forming medium-sized nests in hollow
twigs and stems, or more rarely under the" bark. They are timid and slowmoving insects, often feigning death or dropping rapidly to the ground when disturbed." He has seen them breaking open the earthen tunnels constructed by termites on the trunks of trees and attacking the inmates.
В фауне Вьетнама отмечен один вид - C.simoni E т.: Ханой (Захаров); о-ва Намзу, о. Дау (Курзенко); арх. Байтылонг, о Донгкхо, о.Фонвонг; о.Тям; о.Кондао; о.Тхом (Сиамский залив) (Радченко).
Распространен: Цейлон, Андаманские о-ва (Bolton, 1974); в нашем распоря- жении имеется материал из Индии - Калсимионг (Коровин) и Южного Китая - Ю н ь - нань, 30 км ЮВ Чэли (Панфилов).
Taxonomy. The genus is assigned to the tribe Cataulacini (Bolton 2003). The genus was revised by Bolton (1974, 1982). The worker of the single Vietnamese species ( C. granulatus ) has the following features.
Worker monomorphic; head posteroventrally with an acute angle; frontal lobe and frontal carina extremely developed horizontally; frontal carina touching the ventral margin of eye and reaching to the posterolateral corner of head, and overhanging sides of head; antennal scrobe extremely deep, running below eye, capable of accommodating whole antenna; clypeus with anterolateral corners forming triangular points; posteromedian portion of clypeus widely inserted between frontal lobes; mandible small, triangular, with apical tooth, single preapical tooth and a small blunt denticle followed by a long edentate or bluntly crenulate edge which ends at the basal angle; antenna 11-segmented, with 3-segmented club; scape weakly curved, strongly widened distally and somewhat flattenedwith a very narrow lamella on the leading edge; eye large, located dorsolaterally behind midlength of sides of head; mesosoma in lateral view flattened dorsally; promesonotum marginate, anterodorsally with a sharp edge and dorsolaterally with a dentate edge; promesonotal suture absent dorsally; katepisternum anteriorly with an anterolaterally directed, triangular projection; metanotal groove inconspicuous or almost absent dorsally but conspicuous laterally; propodeal spine well developed as a posterolateral projecting horn; propodeal lobe well developed, blunt-triangular; petiole in lateral view somewhat globular or cuboidal, without distinct anterior peduncle, with distinct subpetiolar process; postpetiole shorter than height, with distinct anteroventral angle; first gastral tergite greatly expanded, comprising whole of gastral dorsum in dorsal view; remaining gastral segments very small, visible only apically and apicoventrally; body strongly sclerotized and sculptured, bearing short, broad and blunt hairs.
Cataulacus is easily distinguished from other myrmicine genera known from Vietnam by antennal scrobe running below eye, frontal lobe and frontal carina extremely developed horizontally, and first gastral tergite greatly expanded, comprising whole of gastral dorsum in dorsal view.
Vietnamese species. One species is known from Vietnam: granulatus Latreille [= sp. eg-1] (BaVi, Cuc Phuong, Nui Chua, My Yen, Tam Dao, Tay Yen Tu, Van Ban).
Bionomics. Cataulacus granulatus nests in hollows within living and dead twigs of trees, and workers forage on vegetation.
Worker. - Length 2 1 / 4 lines. Black; the head, thorax and nodes of the peduncle of the abdomen rugose; the apical portion of the scape, the apex of the flagellum, the anterior tibiae and tarsi, and the apex of the intermediate and posterior tibiae above, pale ferruginous. Head with the sides rounded, narrowed anteriorly, with the anterior margin very slightly emarginate, nearly straight; the margin of the vertex also slightly emarginate and crenu-lated; convex above, and longitudinally and irregularly rugose-striate. Thorax sculptured similarly to the head; the sides spinulose, narrower than the head, widest anteriorly; the metathorax with two stout spines; the legs rugose, covered with short, minute spines, each spine terminating with a pale seta; the spines on the margin of the thorax have also terminal white setae as well as the nodes of the peduncle of the abdomen. Abdomen ovate, slightly emarginate at the base; the base with a number of irregular longitudinal carinae; beyond, it is very delicately carinated, and sprinkled with minute, erect pale setae. (Fig. 11, [[ worker ]] Pl. XL)
Hab. - Singapore.
Formica , pt., Latr. Hist. Nat. Fourm. 275 (1802). Cryptocerus , pt., St. Farg. Hym. i. 171 (1836). Cataulacus , Smith, Mon. Crypt. Trans. Ent. Soc. Lond. 2nd ser. ii. (1853).