Cataulacus

The genus is Palaeotropical with its main diversity centred in the Afrotropical region. The taxonomy of the genus is in a fairly good condition since it was first revised by Bolton (1974a) on a global scale, additional species added later by Snelling (1979) for the Afrotropical region and then Bolton (1982) presented an updated revision with more new species and a species-level key. Most species of this genus are forest-inhabitants while only a minority live in more open and arid habitats. All nest and forage on trees or in the vegetation and several species are known to be trophobiotic, while one species was observed to prey on termites (Arnold, 1917; Bolton, 1974a). Interestingly, many members of this genus often co-occur with more dominant and aggressive ant species from the genera Crematogaster and Oecophylla but are usually well-protected by their heavily armoured exterior or dropping-off behaviour (Bolton, 1974a; Yanoviak et al., 2008).

Identification
Bolton's (1974) - Monomorphic, arboreal myrmicine ants with the head and usually also the body somewhat depressed. Antennae 11-segmented with a 3-segmented club. Palp formula 5,3. Anterior clypeal margin usually notched or impressed medially. Frontal carinae very widely separated, strongly expanded. Antennal scrobes present, running below the large eyes, bounded by the frontal carinae only anterodorsally. First gastral tergite very much enlarged, constituting the entire dorsal gaster in female and worker and the greater portion of the dorsum in the male. Wings always with r-m and m-cu absent, and with M fused to Rs until close to 2r. Male genitalia partially retractile, with cuspis of volsella absent, digitus strongly developed into a broadly T-shaped structure; aedeagus serrate or denticulate ventrally.

Species Groups
Cataulacus species groups

Distribution
Bolton (1974) - The main centres of speciation are the Ethiopian region, particularly the rain forest zones, and the Indonesian and Philippine islands in the Indo-Australian region. Madagascar shares a single species with southern Africa and this and some of its remaining species are members of the now dominant species-group of eastern and southern Africa, the intrudens (F. Smith) group. The rest of the Madagascan fauna is, however, very specialized and not of the intrudens-group. In fact these species are related to huberi E. Andre and its allies, a group predominantly of the West and Central African rain forests. This apparently indicates a double migration of species in the direction Africa → Madagascar, the first consisting of huberi-group species and the second and later migration of intrudens-group forms.

The Indian subcontinent is very poorly populated at species level, only 3 being known, and with a fourth present on Ceylon and the Andaman Islands. Only a single species, granulatus (Latreille), is known to occur in both the Oriental and Indo-Australian regions. The most easterly record of the genus is from Waigeo Is., off north-west New Guinea (Irian Barat), and a marked decrease in the number of species occurs along the Indonesian islands in a west-east direction. The fossil species are known mostly from areas now well outside the range of the genus, namely southern and eastern Europe, and indicate a much wider distribution for the genus during Tertiary times.

Species by Region
Number of species within biogeographic regions, along with the total number of species for each region.

Fossils
Fossils are known from:, , (an unidentified species, Wang et al., 2021).

Abundance
At no point in its range can any species of Cataulacus be considered dominant over other arboreal ant genera, nor are they known to be abundant in absolute numbers over wide areas, but certain species are noticeably much more common within their range than others and where such species occur they may constitute a good proportion of the arboreal ant fauna and are usually quite conspicuous. In this last category may be placed Cataulacus guineensis of the West and Central African forests, Cataulacus intrudens of southern and eastern Africa and Cataulacus granulatus of the Oriental and Indo-Australian regions. (Bolton 1974)

Castes
Monomorphic workers.

Nomenclature

 *  CATAULACUS [Myrmicinae: Cataulacini]
 * Cataulacus Smith, F. 1853: 225. Type-species: Cataulacus taprobanae, by subsequent designation of Bingham, 1903: 120.
 * Cataulacus senior synonym of Otomyrmex: Wheeler, W.M. 1922a: 664; Bolton, 1974a: 1.
 * OTOMYRMEX [junior synonym of Cataulacus]
 * Otomyrmex Forel, 1891b: 147 [as subgenus of Cataulacus]. Type-species: Cataulacus oberthueri, by monotypy.
 * Otomyrmex junior synonym of Cataulacus: Wheeler, W.M. 1922a: 664; Bolton, 1974a: 7.

Worker
Bolton (1974) - Minute to large (TL 2.7 – 11.0), mostly black myrmicine ants; monomorphic although often with a considerable size-range within the species, and with the head and body somewhat dorsoventrally flattened.

Mandibles with 1 to 3 apically situated teeth followed by a row of small to minute denticles or by an unarmed apical (masticatory) margin. Palp formula maxillary 5, labial 3-segmented. Clypeus large, rounded behind, usually notched or with an arcuate impression anteromedially and with the anterolateral corners acute or dentate. Clypeal suture often reduced or faint but rarely completely absent. Frontal carinae widely separated, strongly expanded laterally, reaching almost or quite to the level of the eye where they are almost invariably produced into a preocular tooth. The frontal carinae usually overhang the sides of the head of front of the eye and form the apparent lateral margins of the head in front of the eye in full-face view. Antennal scrobes present, running below the eyes and capable of accommodating the whole antenna. Anteriorly the scrobes are bounded above by the frontal carinae but below and behind the eyes the scrobal margins are constituted of the side wall of the head capsule. Scrobes often bounded below by a carina which terminates in a ventrally-directed tooth posteriorly. Antennae 11-segmented, the three apical funicular segments forming a club. Scape curved and much thicker apically than basally. The eyes are distinct, usually large or very large; ocelli are absent (except in some individuals of latus). Alitrunk usually marginate laterally at least on the pronotum (faint in oberthueri, absent from insularis), the margination often equipped with denticles, spines, teeth or lobiform prominences. Dorsal alitrunk often without sutures but the promesonotal suture may be marked by a faint line or impression. Sutures visible laterally upon the alitrunk; a transverse suture on the mesepisternum nearly always evident. Mesokatepisternum with the anteroventral corner produced into a spine, tooth or tubercle, rarely only an acute angle. Propodeum usually bispinose, more rarely bidentate, unarmed in one species (inermis); metapleurallobes or teeth present at the base of the propodeal declivity. Legs with the femora usually grooved or bicarinate beneath to receive the tibiae. Petiole sessile, with a distinct ventral process; in some species the postpetiole also with such a process. First gastral tergite greatly expanded, comprising the whole of the dorsum of the gaster in dorsal view. First sternite also much enlarged, the remaining segments very reduced, visible apically and apicoventrally. Sting reduced or vestigial, apparently non-functional. Hairs in the species are typically short, broad and blunt but variously specialized in some species, absent in others; almost invariably with 3 to 4 long bristles projecting from the lower border of the eye. Full adult coloration uniform black or black-brown, commonly with the antennae, tibiae and tarsi lighter, yellow or yellow-brown.

Queen
Bolton (1974) - Similar to the worker but the head always with ocelli developed, the alitrunk with flight sclerites and with well-marked dorsal sutures. Gaster usually more elongate than in the worker and often with virtually parallel lateral borders.

Male
Bolton (1974) - Head constructed basically as in worker but with ocelli present. The frontal carinae are not so strongly expanded laterally and in some species the sides of the head proper are visible below the carinae when in dorsal view. Preocular teeth often absent. The head capsule itself is strongly narrowed in front of the large, very prominent eyes. Pronotum well developed, clearly visible in dorsal view and not at all overhung by the mesoscutum. Parapsidal furrows present. Notauli usually with the anterior arms of the Y-shape developed and crossribbed; the posterior arm often little or not developed, rarely as well developed as the anterior arms. Venation as in the female. Propodeum bidentate or bispinose; the petiole and sometimes also the postpetiole more elongate and slender than in the female or worker castes but the ventral processes similarly developed. First gastral tergite very large but not as strongly developed as in the other castes; the following segments usually visible in dorsal view. Genitalia partially retractile, but the highly sclerotized apical portions of the parameres always projecting. In species examined the genitalia had the aedeagus at least strongly serrate ventrally, usually denticulate; volsellae with cuspis absent and the digitus developed into a much enlarged, broadly T-shaped lamelliform structure. The basal portion of each paramere is much less strongly sclerotized than the apical, projecting portion, the latter usually with numerous fine hairs.

Immature Stages
Larva. G. C. Wheeler & J. Wheeler (1960) - body profile elongate-subelliptical, with the head applied to the ventral surface near the anterior end. Under this grouping the Cataulacus larvae were given as cataulaciform; with the body profile straight, elongate-subelliptical; prothorax forming a very short, stout neck which is inclined ventrally to 45 degrees; segmentation indistinct. The mandibles were also described as cataulaciform: roughly trapezium-shaped, the apex forming a slender, short acute tooth which is curved medially; subapical portion of medial border more or less projecting and bearing 2 to 5 minute teeth.

Pupa. Free, not enclosed in cocoons.