Cataulacus vorticus

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Cataulacus vorticus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Crematogastrini
Genus: Cataulacus
Species: C. vorticus
Binomial name
Cataulacus vorticus
Bolton, 1974

Cataulacus vorticus P casent0900272.jpg

Cataulacus vorticus D casent0900272.jpg

Specimen Label

The nest from which Nigerian specimens were taken was situated in and under the bark of a cocoa tree, at the junction of two main branches about 5 ft above ground level. The tree bark on and in the vicinity of the nest was covered with moss.

Identification

A member of the tenuis group. Cataulacus vorticus is closely related to Cataulacus brevisetosus and like that species it possesses clavate cephalic and clypeal hairs. It is separable by the armament of the pronotum which here consists of but a single tooth whilst in brevisetosus there is a row of denticles on each side. (Bolton 1974)

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Afrotropical Region: Kenya, Nigeria (type locality), Uganda.

Distribution based on specimens

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The above specimen data are provided by AntWeb. Please see Cataulacus vorticus for further details

Biology

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)

Castes

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • vorticus. Cataulacus vorticus Bolton, 1974a: 38, figs. 16, 19 (w.q.m.) NIGERIA.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Description

Worker

Holotype. TL 3.5, HL 0.90, HW 0.82, CI 91, EL 0.42, OI 51, IOD 0.64, SL 0.44, SI 54, PW 0.56, AL 0.94, MTL 0.44.

Bolton 1974 fig 15-21
Occiput and vertex meeting through a continuous convexity, occipital crest absent. Occipital corners with a bluntly triangular small tooth and with a denticle close to the tooth upon the occipital margin. Sides of head behind eyes shallowly convex, minutely and irregularly denticulate. Preocular tooth small, broadly triangular, separated from the eye by a smaller, rounded prominence. Pronotum weakly marginate laterally, the humeral angles acute and prominent, dentiform in dorsal view. A single tooth is present on the pronotal margin, close to the junction with the mesonotum. Between the humeral angles and this tooth the margin is smooth, very shallowly concave and without denticles. Sides of mesonotum scarcely or not marginate, without denticles; the propodeum similar and armed with a pair of spines. Dorsal surface of alitrunk without sutures or impressions; sides of alitrunk gradually convergent behind the pronotal tooth. In profile the anterior and posterior surfaces of the petiole strongly convergent dorsally, meeting in what is virtually a right-angle; the petiole without a differentiated dorsal face. Anterior face of postpetiole vertical, the posterior face almost so, the dorsal surface convex. Subpetiolar process simple, with a sharp posteroventral angle. Subpostpetiolar process simple, short, bluntly digitiform. First gastral tergite not marginate laterally.

Dorsum of head with a fine rugoreticulum everywhere, the interspaces finely and densely but shallowly reticulate-punctate, dully shining. Pronotal dorsum similarly but more densely sculptured, the reticulae close together and with a predominantly longitudinal trend. On the mesonotum and propodeal dorsum the rugae are fine and mostly longitudinal, more distinct upon the propodeum; the whole surface finely and quite strongly reticulate-punctate. Declivity of propodeum smooth and shining with scattered, very faint punctures. Petiole with some faint longitudinal rugulae; the postpetiole predominantly densely punctate but with a few faint rugules. First gastral tergite finely and densely reticulate-punctate.

Hairs on clypeus and remainder of the cephalic dorsum strongly clavate, the hairs longer and more distinct upon the clypeus than elsewhere. Dorsal surfaces of alitrunk, pedicel, appendages and gaster with numerous short, very fine, simple hairs, difficult to see on the alitrunk under low magnification.

Paratype. TL 3.4 – 3.5, HL 0.84 – 0.90, HW 0.74 – 0.82, CI 88 - 93, EL 0.38 – 0.44, OI 50 - 54, 10D 0.54 – 0.62, SL 0.40 – 0.44, SI 51 - 54, PW 0.52 – 0.56, AL 0.92 – 0.94, MTL 0.42 – 0.44 (3 measured).

As holotype but in the smallest the sides of the head behind the eyes lack denticles and the humeral angles are not as prominent. The subpetiolar process is clearly visible in one specimen and has the anteroventral angle broadly rounded.

Queen

Paratype. TL 4.2 – 4.4, HL 1.00, HW 0.82 – 0.84, CI 82 - 84, EL 0.44 – 0.46, OI 53 - 55, IOD 0.62 – 0.66, SL 0.44, SI 52 - 54, PW 0.72 – 0.76, AL 1.22 – 1.26, MTL 0.44 – 0.46 (4 measured).

Similar to worker but with denticulation of sides of head behind eyes very much reduced or absent. Humeral angles as well developed as in worker but the tooth near the promesonotal junction absent. Propodeal spines short and blunt. Sculpturation of mesoscutum and propodeal dorsum longitudinal, that of the latter stronger than that of the former.

Male

Paratype. TL 3.8 – 4.0, HL 0.64 – 0.72, HW 0.64 – 0.72, CI 100 - 103, EL 0.28 – 0.34, OI 44 - 47, IOD 0.50 – 0.58, SL 0.28 – 0.30, SI 42 - 44, PW 0.64 – 0.68, AL 1.14 – 1.30, MTL 0.46 – 0.54 (4 measured).

Occipital crest absent; occipital corners acutely angled but not dentate. Sides of head behind eyes not denticulate. Humeral angles acute, dentiform in dorsal view, the remainder of the pronotal margins unarmed, shallowly concave and divergent posteriorly. Anterior arms of notauli strongly developed and cross-ribbed, the posterior arm a very weak impression or absent. Parapsidal furrows very strongly marked, impressed. Sides of remainder of alitrunk not denticulate, the propodeum with a pair of short, acute teeth. Head predominantly rather coarsely reticulate-punctate, with some fine overlying rugulae. Pronotum, mesoscutum and scutellum reticulate-punctate with few or no rugulae. In one specimen the scutum has extensive smooth shiny patches surrounding the apical portions of the parapsidal furrows. Propodeal dorsum longitudinally rugose with reticulate-punctate interspaces; the petiole and usually the postpetiole similarly but much more finely sculptured; or the latter lacking distinct rugulae. First gastral tergite finely and densely reticulate-punctate or merely reticulate, dully shining. Hairs numerous on all dorsal surfaces, everywhere fine and simple.

Holotype Specimen Labels

Type Material

Holotype worker, NIGERIA: Gambari, under bark of cocoa tree, 30.viii.1969 (B. Bolton) (BMNH).

Paratypes. 2 workers, 4 females, 3 males, same data as holotype (BMNH and MCZ, Boston). 1 worker, 1 male, ZAIRE: 91 miles W. of Popokabaka, 2.viii.1957 (E. S. Ross and R. E. Leech) (MCZ, Boston).

References