Cataulacus horridus

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)

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

This taxon was described from Borneo.

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

Nomenclature

 *  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].

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].

Additional References

 * 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.