Cataulacus centrurus

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Cataulacus centrurus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Crematogastrini
Genus: Cataulacus
Species: C. centrurus
Binomial name
Cataulacus centrurus
Bolton, 1982

Cataulacus centrurus P casent0900271.jpg

Cataulacus centrurus D casent0900271.jpg

Specimen Label

Nothing is known about the biology of Cataulacus centrurus.

Identification

A member of the tenuis group. As indicated by the stalked-suborbicular cephalic hairs centrurus belongs to the complex of species centring on Cataulacus brevisetosus, and is most closely related to the smaller Cataulacus moloch. In the latter species the simple pilosity of the alitrunk and gaster is very short and stubble-like, whereas in centrurus it is long and conspicuous. The specialized cephalic hairs of moloch are sparser than in centrurus, have the basal stems of the hairs shorter and the apices less strongly expanded. With the head in profile the specialized hairs immediately in front of the eye have the basal stem longer than the swollen apex in centrurus, shorter than the swollen apex in moloch. In profile the propodeal spines of centrurus have the basal third elevated and the apical two-thirds recurved, a feature not seen in moloch where the spines are exceedingly feebly but evenly curved along their length. Finally, the shape of the subpetiolar process differs in the two species, that of moloch having the posteroventral angle more salient and the ventral surface more concave than in centrurus. (Bolton 1982)

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Afrotropical Region: Cameroun (type locality).


Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Much of the information concerning the biology of Cataulacus species is anecdotal and fragmentary. Arnold (1917) wrote a succinct general overview of Cataulacus biology that still remains quite informative. Arnold reports "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 slow-moving insects, often feigning death or dropping rapidly to the ground when disturbed. As Bingham has remarked in connection with this genus (Fauna Brit. India, Formicidae), these ants have the habit of wandering over the trunks of trees and the leaves in what appears to be a very aimless and languid manner. I have occasionally seen them breaking open the earthen tunnels constructed by termites over the trunks of trees and attack the inmates."

Bolton (1974) expands upon this earlier account - "All known Cataulacus species are arboreal or subarboreal nesters and they predominantly forage on the trees and shrubs in which the nests are situated. Very few appear to come down to ground level but in West Africa the small species Cataulacus pygmaeus and Cataulacus brevisetosus may be found foraging in leaf litter or crossing the ground to ascend a tree other than the one in which the nest is situated. The nests themselves are usually constructed in small hollow twigs or stems by the smaller species and in rotten branches or rotted portions of the tree trunk by the larger species. This is rather a generalization as some small species are known which nest in and under rotten bark (e.g. Cataulacus vorticus) and undoubtedly some of the larger forms will eventually be found inhabiting relatively small cavities in plants.

Various species of the genus in Africa are known to inhabit a variety of galls, acacias and bushes as well as large trees. Numerous species have been found nesting in, and have therefore been often collected from, cocoa in Africa. Some of these species are Cataulacus guineensis, Cataulacus pygmaeus, Cataulacus mocquerysi, Cataulacus egenus, Cataulacus vorticus, Cataulacus brevisetosus, Cataulacus kohli and Cataulacus theobromicola. Feeding habits in the genus are mostly unknown but the present author has noted C. guineensis tending aphids and small coccids.

On the plants ants of the genus Cataulacus often occur together with Oecophylla or species of Crematogaster, and appear to be mostly tolerated (at least they are not evicted) by the majority of these forms. Their defence against attackers of these genera lies primarily in their armoured exterior, but their ultimate escape reaction is to curl up and release their grip on the plant, falling to the ground and thus making their escape. The decision to remain immobile and present an armoured surface or to drop from the plant appears to depend upon the size or persistence of the aggressor; larger attackers usually precipitate the latter reaction, but it has also been noted as a result of persistent and unwanted attention by a series of workers of a small Crematogaster species.

The majority of species are forest-dwelling forms, with relatively few adapted to savannah or veldt conditions. Those which do, however, occur in these zones tend to be very successful in their chosen habitat and often possess a wide distribution. A few species are apparently able to exist in any region of Africa providing the basic essentials of nesting-site and food supply are met with, but on the whole the fauna may be divided into forest and non-forest forms."

Some species have nests that can be protected by a single worker's head, as its shape matches the nest entrance and forms an effective plug.

It has more recently been discovered that some species of Cataulacus are efficient gliders (Cataulacus erinaceus, Cataulacus guineensis, Cataulacus mocquerysi and Cataulacus tardus). Workers exhibit directed movement while in freefall that allows them to glide back to regain a hold on the same tree trunk. (Yanoviak et al. 2005, 2007, 2008)

Castes

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • centrurus. Cataulacus centrurus Bolton, 1982: 359, fig. 33 (w.) CAMEROUN.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Description

Worker

HOLOTYPE WORKER. TL 3.9, HL 1.00, HW 0.92, CI 92, EL 0.47, OI 51, SL 0.48, SI 52, PW 0.70, AL 1.10.

With the head in full-face view the lateral margins of the head behind the eyes denticulate, terminating posteriorly in a short tooth at the occipital corner. Occipital crest absent, the dorsum of the head rounding evenly but narrowly into the occipital surface; the occipital margin itself unarmed except for a small tooth situated close to the tooth at the corner. Eyes relatively large, OI > 50. Alitrunk with promesonotum both longitudinally and transversely convex. In profile the highest point at about the midlength of the pronotum, the remainder sloping evenly downwards posteriorly to the base of the propodeal spines. Anterior strongly curved portion of pronotal dorsum with a number of minute peaks or tubercles from which hairs arise; such peaks absent elsewhere on alitrunk. Tooth at base of mesokatepisternum developed. Propodeal spines in profile with the basal third elevated at an angle of about 45°, the apical two-thirds back-curved. Metapleural lobes low and rounded. With the alitrunk in dorsal view the pronotal corners denticulate and the lateral margins of the pronotum armed with a series of 6-7 regularly spaced triangular denticles. Lateral margins of mesonotum with a pair of small denticles whose bases are fused, situated at approximately the midlength. Following the metanotal identation of the margin the sides of the propodeum are equipped with 2-3 small tubercles. Propodeal spines in dorsal view broad and evenly divergent. Petiole in profile rising to a sharp peak dorsally, behind which the surface slopes evenly downwards to the postpetiolar junction. Subpetiolar process with a bluntly rounded anterior lobe and a weakly developed posteroventral tooth. Postpetiole in profile with its dorsal and posterior surfaces tuberculate and its ventral process simple, short digitiform. First gastral tergite not marginate laterally, conspicuously longer than broad. Dorsum of head finely and evenly reticulate-rugulose, the recticular meshes of irregular size and the rugulae low and rounded. Ground-sculpture in the meshes reduced to an inconspicuous vestigial superficial shagreening, without punctulae. Pronotal dorsum similarly but somewhat more strongly sculptured, the reticulum breaking down on the mesonotum so that the longitudinal component predominates and the cross-meshes are reduced or incomplete. Propodeal dorsum more strongly and predominantly longitudinally rugose, irregular centrally. Transverse rugae are present between the bases of the propodeal spines. Ground-sculpture of alitrunk mostly as head but the mesonotum with some minute and virtually effaced punctulae. Petiole in dorsal view longitudinally rugose, the sculpture converging posteriorly. Postpetiole dorsum irregularly rugulose. First gastral tergite blanketed by fine dense reticulate-punctate sculpture, the basal quarter also with widely spaced fine longitudinal costulae. Behind this level the tergite with scattered short longitudinal rugulae which are very fine and irregular and formed by the alignment of the margins of adjacent punctures. First gastral sternite reticulate-punctate. Sides of pronotum obliquely sulcate, the mesopleuron transversely sulcate and the sides of the propodeum more or less vertically so behind the level of the spiracle. Sides of petiole and postpetiole longitudinally sulcate-rugose. Discounting the long simple hairs which arise round the eyes the entire dorsum of the head thickly clothed with stalked-suborbicular hairs, the stems of the hairs long and fine and holding the suborbicular distal portions well clear of the surface of the head. Occipital surface with a number of elongate narrowly clavate hairs. All remaining dorsal surfaces of body densely clothed with moderately long stout cylindrical simple hairs which are truncated apically; those on the alitrunk and petiole straight, those on the postpetiole and first gastral tergite weakly back-curved. Colour uniform black, glossy; the scapes, tibiae and tarsal segments dull yellow.

Type Material

Cameroun: Nkoemvon, 1979 (D. Jackson) (The Natural History Museum).

References