Only known from the type specimen, nothing is known about the biology of Cataulacus impressus.
A member of the tenuis group. This small but aberrant species is immediately recognizable by the shape of the alitrunk in profile and the presence of a transverse groove upon the occipital surface just dorsal to the foramen.
Keys including this Species
Distribution based on Regional Taxon Lists
Distribution based on AntMaps
Distribution based on AntWeb specimens
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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.
- impressus. Cataulacus impressus Bolton, 1974a: 35 (w.) UGANDA.
Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.
Holotype. TL 3.7, HL 0.90, HW 0.86, CI 96, EL 0.46, OI 53, IOD 0.64, SL 0.44, SI 51, PW 0.70, AL 0.98, MTL 0.46.
Occipital crest absent, the occiput and vertex meeting in a smoothly convex curve. Occipital surface just above the foramen with a marked transverse groove or impression, behind which the remaining thin strip of the occiput juts out over the dorsal portion of the foramen itself. Occipital corners each with a single denticle and flanked internally upon the occipital margin by a larger and more conspicuous denticle. Sides of head behind eyes sparsely and minutely denticulate. Clypeal suture demarcated by a strongly impressed arc. Pronotum strongly marginate laterally, the margins sparsely equipped with small, broadly triangular denticles. Mesonotum and propodeum more weakly marginate than pronotum, denticulate, the propodeum armed with a pair of long, broad, dorsoventrally flattened spines which are nearly parallel, only slightly divergent posteriorly. In dorsal view the sides of the pronotum are parallel, the alitrunk becoming narrower at the mesonotum and again at the propodeum. In profile the posterior portion of the mesonotum curves abruptly downwards to the surface of the propodeum so that the more or less flat surfaces of the two are separated by a short but distinct step. Subpetiolar process apparently with a prominent, rounded anteroventral angle and an acute posteroventral angle which is not, however, produced into a spur. Subpostpetiolar process developed, digitiform, simple. First gastral tergite not marginate laterally.
Head with a fine rugoreticulum, the interspaces of which are finely but shallowly reticulate-punctate and shining. Dorsal alitrunk finely longitudinally rugose, the individual rugae widely separated (i.e. distance separating rugae is greater than the width of the individual rugae), the interspaces finely reticulate-punctate and shining. Cross-meshes very sparse upon the dorsum but present in places. Posterior face of petiole with a few very weak transverse rugulae, otherwise the pedicel irregularly finely rugulose and reticulate-punctate. First gastral tergite finely and quite superficially reticulate-punctate, shining.
All dorsal surfaces of head, body and appendages with numerous stout, erect, blunt hairs.
Holotype worker, UGANDA (without further data) (MCZ, Boston).