Cataulacus oberthueri inhabits in a variety of forest habitats in Madagascar.
- 1 Identification
- 2 Distribution
- 3 Biology
- 4 Castes
- 5 Nomenclature
- 6 References
A member of the huberi group. This species is characterized by its large size, well developed triangular shaped occipital corners, relatively very small eyes and its reduction or loss of numerous 'typically cataulacine' features.
The species appears to be related to two other Madagascan species, Cataulacus regularis and Cataulacus porcatus and these, with the possible inclusion of Cataulacus wasmanni, seem to represent a more ancient radiation upon the island. It should be noted that specialization in these species has been accomplished by a reduction of characters considered typical of the genus as a whole, and this tendency reaches its strongest development in Cataulacus oberthueri. The entirety of the head and alitrunk is devoid of denticulation and almost devoid of standing hairs; the margination of the alitrunk is reduced almost to nothing, with only a vestige remaining on the pronotum; and sculpturation everywhere is strongly reduced. Preocular teeth are absent and the posterior portions of the antennal scrobes are very poorly developed.
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Distribution based on Regional Taxon Lists
Distribution based on AntMaps
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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)
The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.
- oberthueri. Cataulacus (Otomyrmex) oberthueri Emery, in Forel, 1891b: 146, pl. 4, fig. 9 (w.) MADAGASCAR. See also: Bolton, 1974a: 24.
Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.
Bolton (1974) - TL 10.8, HL 2.48, HW 2.76, CI 111, EL 0.60, OI 21, IOD 1.74, SL 1.54, SI 56, PW 1.84, AL 3.2, MTL ca 1.90.
Occipital corners extended posteriorly into a very broadly triangular, acute prominence on each side. In profile these projections are seen to be slightly upcurved. Occipital crest unarmed, incomplete medially where the vertex rounds smoothly into the occiput, but laterally the crest is strongly developed, somewhat translucent, and forming a strong inner border to the occipital prominences. Sides of the head behind eyes not denticulate, the actual margin of the head in full-face view semi-translucent between the posterior margin of the eye and the apex of the prominence at the occipital corner. Preocular teeth absent. Pronotum with a weakly developed, transverse ridge anteriorly, and virtually non-existant lateral margination, the latter represented only by an obtuse angle, best seen on the posterior half of the segment. Remainder of alitrunk not marginate; the entirety of the alitrunk without denticles, spines or lobiform prominences laterally. Propodeum with a pair of long, tapering, acute spines. Track of promesonotal suture indicated by a very shallow, faint impression upon the dorsum. Petiole and postpetiole in profile with low, rounded nodes, paniform, each with a short, spiniform ventral process anteriorly. First gastral tergite without margination.
Dorsal surfaces of head, alitrunk and pedicel finely shagreened throughout with some sparse, fine, longitudinal rugation, especially visible and strongest developed upon the head and the propodeal dorsum. First gastral tergite superficially extremely finely and densely reticulate, dully shining.
Upon the dorsal surfaces of the body stout hairs are present only on the frontal carinae, pedicel and apex of first gastral tergite; they are, however, numerous upon the appendages.
Bolton (1974) - Syntype workers, MADAGASCAR: Tamatave and Alaha Kato (E. Perrot) (MRAC, Tervuren) [examined].
- Bolton, B. 1974a. A revision of the Palaeotropical arboreal ant genus Cataulacus F. Smith (Hymenoptera: Formicidae). Bull. Br. Mus. (Nat. Hist.) Entomol. 30: 1-105 (page 24, see also)
- Forel, A. 1891c. Les Formicides. [part]. In: Grandidier, A. Histoire physique, naturelle, et politique de Madagascar. Volume XX. Histoire naturelle des Hyménoptères. Deuxième partie (28e fascicule). Paris: Hachette et Cie, v + 237 pp. (page 146, pl. 4, fig. 9 worker described)