Cataulacus intrudens

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Cataulacus intrudens
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Crematogastrini
Genus: Cataulacus
Species: C. intrudens
Binomial name
Cataulacus intrudens
(Smith, F., 1876)

Cataulacus-intrudens-MCZ001L.jpg

Cataulacus-intrudens-MCZ001D.jpg

Specimen Label

Synonyms

Cataulacus intrudens nests in twigs and branches of trees and shrubs. Arnold (1917:391) records it from hollow twigs of an acacia, Prins (1965:104) found it nesting in a branch of a red bush-willow, Combretum apiculatum.

Identification

A member of the intrudens group.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Afrotropical Region: Angola, Ethiopia, Kenya, Malawi, Mozambique, Namibia, Somalia, South Africa (type locality), United Republic of Tanzania, Zimbabwe.
Malagasy Region: Madagascar.

Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Abundance

The most common Cataulacus species in southern and eastern Africa.

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

Worker

Queen

Nomenclature

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

  • intrudens. Meranoplus intrudens Smith, F. 1876d: 609, pl. 11, fig. 7 (w.q.m.) SOUTH AFRICA. Combination in Cataulacus: Mayr, 1886c: 364. Senior synonym of batonga, baumi, densipunctatus, foveosquamosus, gazanus, hararicus, intermedius, johannae, pseudotrema, rugosus, subrugosus, umbilicatus and material of the unavailable names krugeri, tangana referred here: Bolton, 1974a: 43; of bulawayensis: Bolton, 1995b: 138.
  • hararicus. Cataulacus hararicus Forel, 1894b: 79 (w.) ETHIOPIA. Junior synonym of intrudens: Bolton, 1974a: 43.
  • rugosus. Cataulacus intrudens var. rugosus Forel, 1894b: 78 (w.) MOZAMBIQUE. Mayr, 1895: 129 (q.). Raised to species: Mayr, 1895: 129; Prins, 1963: 104. Junior synonym of intrudens: Bolton, 1974a: 43.
  • johannae. Cataulacus johannae Forel, 1895c: 250 (w.q.) MADAGASCAR. Junior synonym of intrudens: Bolton, 1974a: 43.
  • baumi. Cataulacus baumi Forel, 1901d: 304 (w.q.m.) ANGOLA. [Also described as new by Forel, 1903e: 560.] Junior synonym of intrudens: Bolton, 1974a: 43.
  • batonga. Cataulacus baumi r. batonga Forel, 1913a: 114 (w.) ZIMBABWE. Junior synonym of intrudens: Bolton, 1974a: 43.
  • subrugosus. Cataulacus rugosus var. subrugosus Santschi, 1914e: 26 (w.) SOUTH AFRICA. Santschi, 1937d: 236 (q.). Junior synonym of intrudens: Bolton, 1974a: 43.
  • bulawayensis. Cataulacus baumi var. bulawayensis Arnold, 1917: 391 (w.q.) ZIMBABWE. [First available use of Cataulacus baumi r. batonga var. bulawayensis Forel, 1914d: 218; unavailable name (Bolton, 1974a: 43).] Junior synonym of intrudens: Bolton, 1995b: 137.
  • intermedius. Cataulacus intrudens st. intermedius Santschi, 1917b: 287 (w.) ZIMBABWE. Junior synonym of intrudens: Bolton, 1974a: 43.
  • densipunctatus. Cataulacus johannae r. densipunctatus Stitz, 1923: 163 (w.) NAMIBIA. Junior synonym of intrudens: Bolton, 1974a: 43.
  • pseudotrema. Cataulacus baumi st. pseudotrema Santschi, 1926b: 244 (w.) TANZANIA. Junior synonym of intrudens: Bolton, 1974a: 43.
  • gazanus. Cataulacus baumi var. gazanus Santschi, 1928f: 208 (w.) MOZAMBIQUE. Junior synonym of intrudens: Bolton, 1974a: 43.
  • foveosquamosus. Cataulacus foveosquamosus Santschi, 1937a: 58, figs. 8, 9 (q.) SOUTH AFRICA. Junior synonym of intrudens: Bolton, 1974a: 43.
  • umbilicatus. Cataulacus umbilicatus Santschi, 1937a: 59, figs. 10-12 (q.) MOZAMBIQUE. Junior synonym of intrudens: Bolton, 1974a: 43.

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

Bolton (1974) - The tremendous variation of this species accounts for the many synonymized names. The majority of these forms were described from variations in head shape or sculpturation, some from even more minor details such as differences in propodeal spine length or in pronotal denticulation. Large workers with female-shaped heads and foveolate sculpturation were responsible for baumi and its subspecies and varieties whilst variation in size and sculpturation account for rugosus and johannae with coarse sculpture on the one hand, and subrugosus and intermedius with finer sculpture on the other. Many of the forms were stated in their original descriptions to be close to Cataulacus intrudens or stated as links between two or more forms. For example, both intermedius and subrugosus were given as intermediates between rugosus and intrudens. As this species is the most common of the genus in southern and eastern Africa it is probably the one which Arnold (1917) had in mind when he wrote that, 'many of the so-called species and races are very closely allied, so much so that I believe a study based on more abundant material will later on serve to reduce the present number of species to a much smaller figure'. In fact, when part 4 of his monograph of South African ants was published, Arnold (1920:403) went so far as to state that there were probably only the nuclei of two species in the area, one of which included baumi, batonga, bulawayensis and intermedius. This observation is now known to be accurate. Santschi (1937a) described the female of the species twice, from two separate localities, basing his descriptions to a large extent upon the very characters which had proved so misleading in the past.

The same mistake was made by Prins who, as late as 1965 described a variety krugeri, differentiating it from rugosus by its, 'slightly longer and more acute epinotal spines and by the sculpture of the abdomen which is less developed'. These are the trifling and intrinsically variable characters so much used by earlier authors and which are responsible for the great proliferation of valueless names in the more variable species of this genus.

Description

Worker

Bolton (1974) - TL 4.3 – 5.1, HL 1.04 – 1.48, HW 1.14 – 1.56, CI 103 - 110, EL 0.42 – 0.54, OI 34 - 40, IOD 0.86 – 1.16, SL 0.52 – 0.68, SI 43 - 47, PW 0.94 – 1.30, AL 1.16 – 1.62, MTL 0.54 – 0.82 (15 measured).

Occipital crest absent, vertex and occiput meeting through an angle, not normally confluent in a curved surface. Occipital corners dentate, with a second tooth or denticle internally upon the margin; often also with a few minute denticles on the angle separating vertex and occiput. Sides of head behind eyes usually denticulate, in a majority of cases noticeably so but sometimes the denticles minute, sometimes reducing in size from occipital corner to eye. Rarely denticles are completely absent. When this occurs the workers generally have a female head-shape. Shape of head very variable. On the one hand is a form which may be regarded as extreme worker-shape, and on the other as extreme female-shape, the latter approaching or the same as that found in most queens of this species. Numerous intermediate forms are known and on occasion both extreme forms may be found in the same nest, along with intermediates. The 'worker-shaped' head usually occurs in smaller individuals, more rarely in large, and is characterized by strong denticulation of the sides behind the eyes, strong anterior convergence of the frontal carinae and convexity of the sides of the head behind the eyes. The 'female-shaped' head always occurs in large individuals and shows reduced or absent denticulation of the sides behind the eyes (variable between workers from the same nest series), a reduced tendency for convergence of the frontal carinae anteriorly and a marked lack of convexity in the sides behind the eyes, so that in some individuals these are almost parallel. Alitrunk marginate laterally, denticulate, the denticles variable in size amongst workers, especially upon the pronotal margins. Propodeum with a pair of spines of variable configuration, but which are usually quite broad and somewhat flattened dorsoventrally. Dorsal alitrunk without sutures. Petiole in profile with a steeply sloping anterior face and a usually less steep posterior face, the latter sometimes shallowly concave. These two faces meeting in an acute angle dorsally and occasionally forming a weak ridge at their junction, the petiole without a developed dorsal surface. Postpetiole with a narrow, rounded dorsal surface separating the anterior and posterior faces. Subpetiolar process simple, usually with the antero- and posteroventral angles blunt, more rarely acute but never with the latter extended as a heel or spur. Subpostpetiolar process small and simple or virtually absent. First gastral tergite not marginate laterally.

Sculpturation extremely variable. The most common form of sculpturation consists of a dense rugoreticulum upon the head and pronotal dorsum with reticulate-punctate interspaces and usually with the reticular meshes shagreened. The rugulae usually tend to assume a more longitudinal direction upon the mesonotum and are often reduced or absent in the middle of this sclerite, being replaced wholly or in part by a fine, dense reticulate-puncturation. Propodeal dorsum usually quite strongly longitudinally rugose with few or no cross-meshes; these rugae noticeably more coarse than those upon the pro- or mesonotum. Propodeal declivity with transverse rugae between the spines. In some specimens the cross-meshes of the cephalic rugoreticulum are very reduced, so that the sculpturation is predominantly longitudinal. Variation from this common sculpturation usually occurs by reduction or intensification of one or more of the components. The most coarsely sculptured forms have the dorsal alitrunk and to a lesser extent the head covered with very coarse, strong, predominantly longitudinal rugae. The most weakly sculptured have the head shagreened with scattered foveolae, and the major portion of the dorsal alitrunk similarly sculptured. Traces of rugation are usually maintained on the propodeal dorsum. In large workers the cephalic sculpturation is often somewhat modified. Many of the rugulae are expanded and flattened, obliterating the smaller interspaces. This results in the appearance of coarse foveolae set in a shagreened surface. The pedicel segments usually show longitudinal rugae but some may be irregularly rugose. First gastral tergite varying from finely reticulate-punctate throughout to coarsely longitudinally rugose with reticulate-punctate interspaces.

Erect hairs present on all dorsal surfaces of head, body and appendages but very short and inconspicuous upon the clypeus and cephalic dorsum, and also on the pronotum, where they are usually reduced to very short, stout stubs or even stud-like vestiges.

Queen

Bolton (1974) - TL 6.2 – 7.4, HL 1.20 – 1.60, HW 1.24 – 1.66, CI 96 - 103, EL 0.46 – 0.60, OI 35 - 39, IOD 1.00 - 1.30, SL 0.60 - 0.76, SI 46 - 48, PW 1.20 - 1.50, AL 1.70 – 2.10, MTL 0.66 – 0.86 (5 measured).

Head shape as described above for large female-like workers, very rarely shaped similarly to the typical head form of smaller workers. Denticulation of the sides of the head behind the eyes reduced or absent, as is the denticulation of the alitrunk margins. Propodeal spines reduced, proportionately broader and shorter than in the worker. Sculptural variation as described above.

Male

Bolton (1974) - TL 5.3 -5.7, HL 1.12- 1.20, HW 1.22 – 1.28, CI 106 - 109, EL 0.44, OI 34 - 36, IOD 0.94 – 0.96, SL 0.54 - 0.56, SI 43 - 44, PW 1.06 – 1.08, AL 1.74 – 1.82, MTL 0.68 – 0.72 (3 measured).

Head shape similar to small worker, the sides of the head behind the eyes dentate. Pronotum marginate laterally but not denticulate, similarly with the propodeal margins. Propodeal spines short, blunt and very stout. Parapsidal furrows distinct, the notauli acutely V-shaped rather than Y -shaped, with the posterior portion distinct to the margin of the scutellum. Dorsum of head finely and very densely reticulate-rugose, the longitudinal constituents predominating and more emphasized than the transverse; the interspaces reticulate-punctate. Pronotum similarly but more loosely sculptured, the mesoscutum with only a few weak rugulae, predominantly reticulate-punctate. Scutellum and propodeal dorsum with a rather coarse rugoreticulum. Pedicel longitudinally rugose, gaster finely and densely reticulate-punctate. All dorsal surfaces of head, body and appendages with numerous hairs.

Type Material

Bolton (1974) - LECTOTYPE worker, SOUTH AFRICA: Natal, Durban, Weenen District, in acacia thorns (J. M. Hutchinson) (BMNH), here designated [examined].

During the search for the types of this species a single specimen (a male) was found at UM, Oxford which was marked 'type'. However, the date of collection upon the labels was 1879, proving that it was not of the type series as the species was described in 1876.

Amongst the numerous unnamed specimens of the F. Smith collection in the BMNH were five specimens of intrudens (3 workers, 2 males) each bearing only a single small data label, inscribed '76, 48. Natal'. This reference was checked against volume 4 of the British Museum Zoological Accessions (1864 1881), and on page 214, under '1876 no. 48' was the information: "Meranoplus intrudens. Natal. Presented by F. Smith. This species was found by Mr J. Monkhouse Hutchinson inhabiting thorns of a species of Acacia in the Weenen District, Natal." This is exactly the information given by Smith in the original description of the species and it is concluded that these five specimens represent the type-series.

These have presently been designated lectotype (worker) and paralectotypes (2 workers, 2 males) and will be deposited in BMNH and MCZ, Boston. There is no trace of the female described by Smith, and this is presumed lost or destroyed.

References

  • 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 43, Senior synonym of batonga, baumi, densipunctatus, foveosquamosus, gazanus, hararicus, intermedius, johannae, pseudotrema, rugosus, subrugosus, umbilicatus; and material of the unavailable names krugeri and tangana referred here: )
  • Bolton, B. 1995b. A new general catalogue of the ants of the world. Cambridge, Mass.: Harvard University Press, 504 pp. (page 138, Senior synonym of bulawayensis)
  • Forel, A. 1894b. Abessinische und andere afrikanische Ameisen, gesammelt von Herrn Ingenieur Alfred Ilg, von Herrn Dr. Liengme, von Herrn Pfarrer Missionar P. Berthoud, Herrn Dr. Arth. Müller etc. Mitt. Schweiz. Entomol. Ges. 9: 64-100 PDF
  • Mayr, G. 1886c. Notizen über die Formiciden-Sammlung des British Museum in London. Verh. K-K. Zool.-Bot. Ges. Wien 36: 353-368 (page 364, Combination in Cataulacus)
  • Smith, F. 1876d. Descriptions of new species of Cryptoceridae, belonging to the genera Cryptocerus, Meranoplus, and Cataulacus. Trans. Entomol. Soc. Lond. 1876: 603-612 (page 609, pl. 11, fig. 7 worker, queen, male described)