Nothing is known about the biology of Cataulacus inermis.
A member of the huberi group. The structure and sculpturation of the pedicel ally this species very closely with Cataulacus lobatus, from which it is separable by its lack of propodeal spines and presence of transverse sculpturation upon the propodeal dorsum. In lobatus propodeal spines are present and the sculpturation of the dorsum of the segment is longitudinal where developed. (Bolton 1974)
Keys including this Species
Known from Democratic Republic of Congo amd Gabon.
Distribution based on Regional Taxon Lists
Distribution based on AntMaps
Distribution based on AntWeb specimens
Check data from AntWeb
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.
- inermis. Cataulacus inermis Santschi, 1924b: 218, fig. 10 (w.) DEMOCRATIC REPUBLIC OF CONGO. See also: Bolton, 1974a: 21.
Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.
Bolton (1974) - TL 6.1, HL 1.50, HW 1.74, CI 1l6, EL 0.50, OI 29, IOD 1.42, SL 0.84, SI 48, PW 1.60, AL 1.82, MTL 1.00.
Occipital crest not developed medially, the vertex separated from the occiput by a sharp angle. Occipital corners forming a blunt right-angle, without a tooth or denticle. Sides of head behind eyes not denticulate. Pronotum strongly marginate laterally, the margins expanded and quite regular, not denticulate. Remainder of alitrunk not marginate not denticulate, the propodeum without spines or teeth posterodorsally, the dorsum curving without interruption inio the declivity. Petiole more or less flat dorsally; the postpetiole divided into two lobes dorsally by a median longitudinal impression. First gastral tergite marginate basally and laterally to the level of the spiracle, behind which the margination peters out.
Dorsal surfaces of head and alitrunk very finely and densely reticulate-punctate. On the head there is some faint rugoreticulation, best developed behind the eyes. Pronotum and mesonotum with sparse, scattered, very faint and predominantly longitudinal rugulae. Propodeal dorsum and declivity distinctly and regularly transversely rugulose. Dorsum of petiole and anterior face of postpetiole strongly, rather coarsely longitudinally sulcate. First gastral tergite finely and very densely reticulate-punctate with a scattered rugoreticulum.
Erect hairs absent from alitrunk and from dorsum of head except for a row running between the eyes and the occipital corners and some upon the frontal carinae. Petiole and postpetiole with sparse, very stout hairs; first gastral tergite without hairs except for a few at the apex.
Bolton (1974) - Holotype worker, ZAIRE: Kasai, Ngombe, 5.xi.1921 (H. Schouteden) (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. PDF (page 21, see also)
- Santschi, F. 1924b. Descriptions de nouveaux Formicides africains et notes diverses. II. Rev. Zool. Afr. (Bruss.) 12: 195-224 (page 218, fig. 10 worker described)