Cataulacus horridus

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Cataulacus horridus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Crematogastrini
Genus: Cataulacus
Species: C. horridus
Binomial name
Cataulacus horridus
Smith, F., 1857

Cataulacus insularis P casent0217825.jpg

Cataulacus insularis D casent0217825.jpg

Specimen Label

Synonyms

Cataulacus horridus has large polydomous colonies with thousands of workers. There nests are found in rotten logs. (Maschwitz and Moog 2000).

Identification

One of the largest species of the Indo-Australian and Oriental regions and certainly one of the most easily recognizable. The great development of spines at the occipital corners and the lack of alitrunk margination immediately sets the species aside from its congeners. (as per Bolton, 1974 under insularis, a junior synonym of horridus)

Keys including this Species

Distribution

Known from Borneo, Indonesia (Sumatra), Singapore and West Malaysia.

Distribution based on Regional Taxon Lists

Indo-Australian Region: Borneo (type locality), Indonesia, Malaysia.
Oriental Region: Thailand.

Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

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)

Genetics

Polymorphic microsatellites have been identified for this species. (Debout et al. 2002)

Castes

Nomenclature

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

  • horridus. Cataulacus horridus Smith, F. 1857a: 81, pl. 2, fig. 3 (w.) BORNEO. Crawley, 1924: 401 (q.); Wheeler, G.C. & Wheeler, J. 1954b: 151 (l.). Senior synonym of insularis: Wheeler, W.M. 1919e: 93; Bolton, 1974a: 84. [Bolton gave priority to insularis but priority should rightly be given to horridus, on first reviser principle based on Wheeler's attribution: Bolton, 1995b: 138.]
  • insularis. Cataulacus insularis Smith, F. 1857a: 80, pl. 2, fig. 4 (m.) BORNEO. Junior synonym of horridus: Wheeler, W.M. 1919e: 93; Bolton, 1974a: 84 [see note under horridus].

The following notes on F. Smith type specimens have been provided by Barry Bolton (details):

Cataulacus horridus

Two worker syntypes in Oxford University Museum of Natural History, two worker syntypes in The Natural History Museum. All labelled “SAR.” except for one in Oxford University Museum of Natural History that is “Mal. 23.” Both localities are given by Smith in the original description.

Cataulacus insularis

Holotype male in Oxford University Museum of Natural History. Labelled “SAR.”

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

Description

Worker

Length 3 lines. Black; the antennae short, thick and clavate; the apex rufo-testaceous; head reticulated, produced before the eyes and widely truncated, the lateral angles of the truncation rounded; the lateral margins with a short spine before the eyes; the vertex with the posterior margin emarginate its entire width, forming at the lateral angles large acute spines. Thorax: ruggedly sculptured on the disk, narrowed to the apex of the mesothorax, which is separated from the hinder portion by a deep transverse incision; produced posteriorly at the angles into long, stout, acute spines; the nodes of the abdomen rugose; abdomen rounded, emarginate and striated at the base; the entire insect sprinkled with short erect white setae.

Bolton (1974) - TL 4.8 – 7.0, HL 1.22 – 1.62, HW 1.38 – 1.80, CI 111 - 113, EL 0.46 – 0.56, OI 31 - 32, IOD 1.08 – 1.36, SL 0.76 – 1.00, SI 49 - 56, PW 1.00 – 1.36, AL 1.44 – 1.94, MTL 0.84 – 1.15 (10 measured).

Occipital crest absent; occipital corners prolonged into a pair of massive, subtriangular, broad, acute spines. Sides of head behind eyes denticulate, the denticles also present on the outer edges of the occipital spines and occasionally on the inner edges also. Alitrunk not marginate laterally, the dorsum rounding into the sides, but with a distinct, rather massive, broad tubercle on each side at the level of the promesonotal junction which may represent the last vestige of an ancestral margination. In profile the promesonotum forming a more or less continuous convexity and with a distinct step posteriorly at its junction with the propodeum; the dorsum of the latter on a lower level than that of the former. Propodeum with a pair of very long spines, broad at the base and tapering to an acute apex. Mesokatepisternum developed into a large tuberculiform structure projecting laterally and visible in dorsal view. Gaster not marginate laterally.

Head reticulate-rugose, the interspaces reticulate-punctate. Dorsum of alitrunk very coarsely reticulate-foveolate with a fine reticulate-puncturation everywhere except the apical portions of the propodeal spines which are smooth and shiny. The sculpturation of the alitrunk is usually coarser and more rough-looking in larger individuals than in smaller. Gaster with a fine, dense rugoreticulum and reticulate-punctate interspaces, and usually also with a number of strong, longitudinal basigastric costulae.

All dorsal surfaces of head, alitrunk, gaster and appendages with numerous hairs.

Queen

Bolton (1974) - TL 6.8 – 7.8, HL 1.60 – 1.74, HW 1.80 – 2.00, CI 112 - 115, EL 0.52 – 0.60, OI 29 - 30, IOD 1.36 – 1.50, SL 1.02 – 1.08, SI 54 - 57, PW 1.60 – 1.70, AL 2.30 – 2.50, MTL 1.16 – 1.22 (3 measured).

As worker but the lateral tubercle of the alitrunk reduced to a low, broad swelling, less distinct than in the worker. A similar reduction is seen in the tubercle of the mesokatepisternum, whose apex is directed more anteriorly than in the above. Propodeal spines less well developed, very broad at the base, tapering rapidly to an acute apex. Sculpturation of head and pronotum as in worker, but the mesonotal sclerites and propodeal dorsum are longitudinally rugose; those on the propodeum diverging onto the basal parts of the spines.

Male

Bolton (1974) - TL 6.4 – 6.6, HL 1.30 – 1.34, HW 1.42 – 1.58, CI l09 - 117, EL 0.48 – 0.50, OI 32 - 34, IOD 1.18 – 1.22, SL 0.88 – 0.90, SI 55 - 63, PW 1.30 – 1.32, AL 2.12 – 2.14, MTL 1.08 – 1.12 (z measured).

Occipital spines proportionately as well developed as in worker, the sides of the head behind the eyes denticulate, as are the inner and outer borders of the occipital spines. Preocular tooth absent or reduced to a minute triangular prominence. Lateral tubercle of alitrunk not developed, but the tubercle of the mesokatepisternum distinct, directed forwards as in the female. Anterior arms of notauli distinct, the posterior arm reduced to a mere impression, not shining nor cross-ribbed like the anterior arms. Propodeal spines strongly developed, long and acute. Head reticulate-rugose with punctate interspaces, the rugae either longitudinal to the level of the posterior margin of the eyes and then becoming transverse, so that they form a broad arch around the ocelli, or irregularly distributed over the head.

Type Material

Holotype male, BORNEO: Sarawak (A. R. Wallace) (UM, Oxford,) [examined].

Cataulacus horridus Holotype worker, BORNEO: Sarawak (A. R. Wallace) (UM, Oxford) [examined].

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 84, Senior synonym of insularis)
  • Crawley, W. C. 1924a. Ants from Sumatra, with biological notes by Edward Jacobson. Ann. Mag. Nat. Hist. 9(13): 380-409 (page 401, queen described)
  • Debout, G., A. Dalecky, et al. 2002. "Isolation and characterization of polymorphic microsatellites in the tropical plant-ant Cataulacus mckeyi (Formicidae: Myrmicinae)." Mol. Ecol. Notes 2: 459-461.
  • Maschwitz U. and Moog J, 2000. Communal peeing: a new mode of flood control in ants. Naturwissenschaften. 87(12):563-565.
  • Smith, F. 1857a. Catalogue of the hymenopterous insects collected at Sarawak, Borneo; Mount Ophir, Malacca; and at Singapore, by A. R. Wallace. [part]. J. Proc. Linn. Soc. Lond. Zool. 2: 42-88 (page 81, pl. 2, fig. 3 worker described)
  • Wheeler, G. C.; Wheeler, J. 1954b. The ant larvae of the myrmicine tribes Cataulacini and Cephalotini. J. Wash. Acad. Sci. 44: 149-157 (page 151, larva described)
  • Wheeler, W. M. 1919f. The ants of Borneo. Bull. Mus. Comp. Zool. 63: 43-147 (page 93, Senior synonym of insularis)