| Cataulacus pygmaeus|
Nests are made in stems or twigs of low shrubs or trees and the workers forage freely upon the plant. Small coccids are tended on the apical portions of twigs or flower stalks.
A member of the intrudens group. C. pygmaeus is separated from species closely related to brevisetosus by its relatively small eyes (01 < 50) and loose, very fine reticulate-rugose sculpturation upon the head and alitrunk, in which the meshes are widely separated. Some individuals of Cataulacus pygmaeus, with cephalic hairs gradually increased in thickness from base to apex, may be confused with Cataulacus brevisetosus. Notes on the separation of such forms from true brevisetosus are given under that species. (Bolton 1974)
Keys including this Species
Although pygmaeus is very widespread in Africa its distribution seems mostly confined to savannah regions or open wooded areas, but it is also known from forests (Bolton 1974).
Distribution based on Regional Taxon Lists
Distribution based on specimens
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.
- pygmaeus. Cataulacus pygmaeus André, 1890: 325 (w.) SIERRA LEONE. Senior synonym of bakusuensis, chariensis: Bolton, 1974a: 48.
- chariensis. Cataulacus pygmaeus var. chariensis Santschi, 1911c: 358 (w.) CHAD. Junior synonym of pygmaeus: Bolton, 1974a: 48.
- bakusuensis. Cataulacus pygmaeus var. bakusuensis Forel, 1913h: 350 (w.m.) DEMOCRATIC REPUBLIC OF CONGO. Junior synonym of pygmaeus: Bolton, 1974a: 48.
Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.
Bolton (1974) - TL 3.7 – 4.4, HL 0.94 – 1.10, HW 0.92 – 1.06, CI 94 - 97, EL 0.40 – 0.46, OI 41 - 46, IOD 0.72 – 0.84, SL 0.48 – 0.52, SI 49 - 51, PW 0.72 – 0.90. AL 1.01 – 1.26, MTL 0.48 – 0.56 (15 measured).
Dorsum of head with a fine loose rugoreticulum, rarely with the longitudinal component predominating. Interspaces finely, densely and rather faintly reticulate-punctate, the surface somewhat shining. Pronotal dorsum with a rugoreticulum, coarser than that of the head, the meshes widely spaced, the interspaces reticulate-punctate and dully shining. On the mesonotum and propodeal dorsum there is a tendency for the cross-meshes of the reticulum to disappear, leaving a fine, widely spaced and irregular longitudinal rugation. First gastral tergite densely reticulate-punctate, with fine rugulae everywhere upon the disc of the sclerite, predominantly or wholly longitudinal in direction.
Dorsal surfaces of head, body and appendages with numerous short, stout, simple hairs. Rarely these hairs are increased in thickness from base to apex upon the cephalic dorsum.
Bolton (1974) - TL 5.2 – 5.3, HL 1.14 – 1.16, HW 1.08, CI 92 - 95, EL 0.44 – 0.38, OI 40 - 46, IOD 0.80 – 0.84, SL 0.52 – 0.54, SI 48 - 50, PW 0.96 – 0.98, AL 1.48 – 1.50, MTL ca 0.62 (3 measured).
As worker, with the usual modification of the alitrunk for flight. Denticulation of the sides of the head behind the eyes and often of the pronotal margins reduced, sometimes absent from the former. Mesoscutum with marked longitudinal rugation, with few or no cross-meshes.
Bolton (1974) - TL 4.2 – 4.3, HL 0.84 – 0.86, HW 0.90 – 0.92, CI 105 - 109, EL 0.38, OI 41 - 42, IOD 0.66 – 0.72, SL ca 0.44, SI 47 - 49, PW 0.74 – 0.78, AL 1.34 – 1.36, MTL ca 0.58 (2 measured).
Occipital crest absent, occipital corners denticulate and with a second denticle on the occipital margin close to the corners. Sides of head behind eyes denticulate. Preocular tooth reduced to a mere angle or absent. Pronotal margins irregular but not denticulate. Anterior arms of notauli well developed and cross-ribbed, the posterior arm absent or its track marked by a faint impression. Propodeal spines reduced to a pair of acute teeth. Dorsum of head predominantly reticulate-punctate with a few very fine longitudinal rugulae and a weak reticulum close to and behind the eyes. Pronotum similarly sculptured but with a very loose rugoreticulum everywhere, the meshes widely spaced. Mesoscutum quite strongly reticulate-punctate with a few longitudinal rugulae. Propodeal dorsum reticulate-rugose, the rugae here stronger than anywhere else upon the dorsal alitrunk or head. First gastral tergite finely reticulate or superficially reticulate-punctate, shining. Simple erect hairs present on all dorsal surfaces of the head and body.
Holotype worker, SIERRA LEONE (A. Mocquerys) (MNHN, Paris) [examined].
Cataulacus pygmaeus var. chariensis Holotype worker, CHAD: Moyen Chari, Fort Archambault (J. Decorse) (MNHN, Paris) [examined].
Cataulacus pygmaeus var. bakusuensis Syntype female, male, ZAIRE: Bakusu, dans un rameau (MRAC, Tervuren) [examined].
Cataulacus traegaordhi Syntype workers, male, female, SOUTH AFRICA: Natal, Zululand, Dukudu, 27.vii.1905 (1. Tragardh) (NM, Basle; MRAC, Tervuren) [examined].
Cataulacus tragardhi [sic] var. ugandensis Syntype workers, UGANDA: Unyoro Prov., near Hoima, i.1909 (Ch. Alluand) (NM, Basle) [examined].
?Cataulacus marleyi Syntype workers, SOUTH AFRICA: Natal, Krants Kloof (H. B. Marley) (location of types not known). (Provisional synonym, see below.)
Cataulacus jeanneli var. aethiops Syntype workers, ZAIRE: Kidada-Kitobola, 14/25.ii.1922 (H. Schouteden), and Barumbu (Bequaert) (MRAC. Tervuren) [examined].
Cataulacus pygmaeus subsp. suddensis Syntype workers, male, SUDAN: Upper White Nile, Adok, in the Sudd, IO.vii.I939 (N. A. Weber) (probably in AMNH, New York).
- André, E. 1890. Matériaux pour servir à la faune myrmécologique de Sierra-Leone (Afrique occidentale). Rev. Entomol. (Caen) 9: 311-327 PDF
- 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 48, Senior synonym of bakusuensis and chariensis)