Nothing is known about the biology of Cataulacus difficilis.
A member of the tenuis group. Santschi originally associated this species with Cataulacus pygmaeus, but the development of the mesokatepisternal tooth in the type (and only known) worker quickly separates this form. In proportion to the overall size of the individual this tooth is almost as well developed as in the better known species Cataulacus micans, Furthermore, the dimensions and characteristics of the species show it to be more closely related to Cataulacus brevisetosus than to pygmaeus. (Bolton 1974)
Keys including this Species
Known from Benin and Cameroon.
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.
- difficilis. Cataulacus pygmaeus st. difficilis Santschi, 1916b: 506 (w.) BENIN. Raised to species: Bolton, 1974a: 33.
Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.
Bolton (1974) - TL 3.3, HL 0.86, HW 0.78, CI 91, EL 0.42, OI 54, IOD 0.58, SL 0.44, SI 56, PW 0.64, AL 0.90, MTL not measurable.
Occipital crest absent; occipital corners each with a pair of small but acute, triangular teeth, one situated at the corner itself, the second just internal to it upon the occipital margin. Sides of head behind the large eyes relatively short but strongly denticulate. Sides of pronotum marginate, strongly denticulate, the remainder of the alitrunk more weakly and sparsely denticulate. Propodeum with a pair of short, acute, divergent spines. Dorsal alitrunk without trace of sutures. Mesokatepisternal tooth strongly developed, triangular, acute and projecting distinctly when the alitrunk is viewed from above. Subpostpetiolar process long and digitiform (subpetiolar process obscured by glue on type). First gastral tergite not marginate laterally.
Dorsum of head finely and shallowly recticulate-rugose, the rugae becoming longitudinal anteriorly. The interspaces of the rugoreticulum sparsely and very shallowly reticulate-punctate, shining, in places the puncturation almost effaced. Pronotal dorsum similarly sculptured but on the mesonotum and propodeal dorsum the cross-meshes are lost, so that the rugae run longitudinally. First gastral tergite strongly and rather coarsely reticulate-punctate, much more strongly so than the head or dorsal alitrunk.
Stout, blunt, erect hairs present upon all dorsal surfaces, simple, relatively long and most abundant upon the head.
Bolton (1974) - Holotype worker, DAHOMEY (Desanti) (NM, Basle) [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
- Santschi, F. 1916b . Descriptions de fourmis nouvelles d'Afrique et d'Amérique. Ann. Soc. Entomol. Fr. 84: 497-513 (page 506, worker described)