Key to Cataulacus of the Indo-Australian and Oriental Regions

This key is based on Bolton's world revision of the genus: Bolton, B. 1974. A revision of the Palaeotropical arboreal ant genus Cataulacus F. Smith (Hymenoptera: Formicidae). Bulletin of the British Museum (Natural History) Entomology. 30:1-105.

A revised key to the Afrotropical species was published by Bolton in 1982 (Bolton, B. 1982. "Afrotropical species of the myrmicine ant genera Cardiocondyla, Leptothorax, Melissotarsus, Messor and Cataulacus (Formicidae)." Bulletin of the British Museum (Natural History) Entomology. 45:307-370). That key provided revisions that reflected revisionary changes of the African fauna. Afrotropical species should be keyed out using this 1982 Key to Afrotropical Cataulacus Species.

The 1974 key is the only such resource for Malagasy species: Key to Cataulacus of the Malagasy Region. There are now known to be a few undescribed species in the region that are not accounted for in this key.

The key to Indo-Australian and Oriental species is given below.

Key to the Species of the Indo-Australian and Oriental Regions
Key to workers. Note: the worker of longinodus is not known.

IO-1

 * Sides of alitrunk without margination, the dorsum rounding into the sides and with a laterally projecting, broad, blunt tubercle at the level of the promesonotal junction. Occipital corners drawn out into a pair of long, acute, broadly triangular spines. Sculpturation on dorsum of alitrunk an extremely coarse foveolate-rugulation with a superimposed fine reticulate-puncturation. (West Malaysia, Borneo, Sumatra) . . . . . Cataulacus insularis (now a junior synonym of Cataulacus horridus)


 * Sides of alitrunk marginate, at least on the pronotum; the margination consisting of a flange, ridge or acute angle, often denticulate separating the dorsum from the sides. No laterally projecting, broad, blunt tubercle present at the level of the promesonotal junction. Occipital corners usually dentate but never projecting as above. Sculpturation of dorsal alitrunk finer, usually a reticulate-rugulation and a fine and dense puncturation . . . . . IO-2

IO-2
return to couplet #IO-1
 * Larger, very broad species, HL > 1.35 (usually 1.50 or more), HW > 1.60, IOD > 1.30, with relatively very small eyes, OI < 25 . . . . . IO-3


 * Smaller, less broad species, HL < 1.35, HW < 1.60, IOD 1.20 or less, with relatively larger eyes, OI > 25 . . . . . IO-4

IO-3
return to couplet #IO-2
 * First gastral tergite sharply marginate laterally throughout its length. Lateral margins of pronotum and propodeal spines expanded into broad, projecting flanges or plates. Very broad-headed species CI > 140 (West Malaysia, Singapore, Borneo, Sumatra) . . . . . Cataulacus latissimus


 * First gastral tergite without lateral margination. Lateral margins of pronotum and propodeal spines not expanded into broad, projecting flanges or plates. Less broad-headed species, CI < 135. (India, Burma) . . . . . Cataulacus latus

IO-4
return to couplet #IO-2
 * Dorsum of head behind clypeus and dorsum of pronotum without short, erect hairs; a few short hairs may be present around the eyes and on the margins of the head and alitrunk, projecting laterally. In profile the pronotal dorsum usually without minute, raised peaks or tubercles . . . . . IO-5


 * Dorsum of head behind clypeus and usually dorsum of pronotum with numerous short, erect hairs, either simple or clavate; these are also present on the margins of the head and alitrunk, projecting laterally. In profile the pronotal dorsum with a number of minute raised peaks or tubercles, especially on the anterior half . . . . . IO-8

IO-5
return to couplet #IO-4
 * First gastral tergite marginate laterally, the margination consisting of a ridge or acute angle separating the dorsum of the sclerite from the sides . . . . . IO-6


 * First gastral tergite not marginate laterally, the dorsum of the sclerite rounding into the sides . . . . . IO-7

IO-6
return to couplet #IO-5
 * Occipital crest complete, raised medially into a projecting ridge (Text-fig. 36). Mesonotum covered with a fine rugoreticulum. Dorsal surfaces of femora without stout, erect hairs.  Smaller species, HW < 1.15, CI < 112, IOD < 0.85. (West Malaysia, Borneo, Sumatra) . . . . . Cataulacus praetextus


 * Occipital crest complete and sharp but not raised medially into a projecting ridge (Text-fig. 37). Mesonotum with regular, more or less parallel longitudinal rugae. Dorsal surfaces of femora with distinct stout, blunt, erect hairs.  Larger species HW > 1.20, CI > 112, IOD > 0.90.  (Philippines) . . . . . Cataulacus catuvolcus

IO-7
return to couplet #IO-5
 * Occipital crest complete, the median portion raised into a low, posteriorly projecting ridge (Text-fig. 35). Entirety of dorsal alitrunk covered with a fine rugoreticulum. (Borneo) . . . . . Cataulacus reticulatus


 * Occipital crest absent, the dorsum of the head curving into the occiput. Dorsum of pronotum with a rugoreticulum but the mesonotum and propodeum with a series of regular, approximately parallel, longitudinal rugae. (Philippines) . . . . . Cataulacus chapmani

IO-8
return to couplet #IO-4
 * Propodeal spines long, divergent, broad at the base and gradually tapering apically (Text-figs. 31, 41); each spine distinctly longer than half of the basal distance separating it from its twin, usually as long or longer than the complete distance separating the spines . . . . . IO-9


 * Propodeal spines short to virtually absent; weakly or not at all divergent, slightly or hardly tapering from base to apex, usually widely separated, and each spine is usually shorter than half the basal distance separating it from its twin (Text-figs. 38, 39) . . . . . IO-12

IO-9
return to couplet #IO-8
 * On the dorsum of the alitrunk the reticulate-rugulation tending to lose its cross-meshes and to become effaced on the mesonotum where it is secondary to a fine, dense reticulate-puncturation. Dorsa of the alitrunk and pedicel with only a few scattered, short, thick erect hairs, very indistinct . . . . . IO-10


 * On the dorsum of the alitrunk the reticulate-rugulation coarse and distinct over the entire surface, not fading out nor becoming secondary to a reticulate-puncturation on the mesonotum. Dorsa of the alitrunk and pedicel with numerous distinct, short erect hairs, very conspicuous . . . . . IO-11

IO-10
return to couplet #IO-9
 * In profile the mesonotum forming a short but distinct step at its junction with the propodeum. Pronotum on each side with a prominent rectangular flange, denticulate on its outer margin (Text-fig. 31). The mesonotum with a number of regular, parallel, low, longitudinal rugae. (Sulawesi) . . . . . Cataulacus flagitiosus


 * In profile the dorsa of the mesonotum and propodeum forming a continuous convexity at their junction. Pronotum denticulate on each side but without a prominent rectangular flange (Text-fig. 32). The mesonotum without regular, parallel, low, longitudinal rugae. (India, Ceylon) . . . . . Cataulacus taprobanae

IO-11
return to couplet #IO-9
 * First gastral tergite finely longitudinally rugose throughout its length over the entire surface of the sclerite, the rugae distinct on the centre of the disc. Head longer, HL > 1.10, CI 105 or less. (Java) . . . . . Cataulacus nenassus


 * First gastral tergite not finely longitudinally rugose throughout its length over the entire surface of the sclerite; at least the disc not rugose. Head shorter, HL < 1.10, CI 109 or more. (Philippines, Moluccas, New Guinea: Waigo Islands) . . . . . Cataulacus setosus

IO-12
return to couplet #IO-8
 * Propodeal spines represented by a pair of small, obtuse, blunt tubercles. Node of petiole in dorsal view distinctly longer than broad. (Burma) . . . . . Cataulacus muticus


 * Propodeal spines distinct; of very short or dentiform they are acute and the node of the petiole in dorsal view is broader than long . . . . . IO-13

IO-13
return to couplet #IO-12
 * Hairs on dorsum of head and on clypeus very short, clavate or subglobose. Sculpturation of mesonotum and propodeal dorsum predominantly of longitudinal rugae. In dorsal view the alitrunk without a distinct notch or constriction between the mesonotum and the propodeum. Small species, HL 1.00 or less, PW < 0.90, with relatively large eyes, OI > 36. (Ceylon, Andaman Islands) . . . . . Cataulacus simoni


 * Hairs on dorsum of head and on clypeus usually relatively long, simple, stout and blunt. If some cephalic hairs are clavate then the sculpturation of the mesonotum and propodeal dorsum is predominantly a rugoreticulum and in dorsal view the alitrunk has a distinct notch or constriction between the mesonotum and propodeum. Larger species, HL > 1.00, PW > 0.95, with relatively small eyes, OI < 36 . . . . . IO-14

IO-14
return to couplet #IO-13
 * Subpetiolar process complex; anteroventrally with a bluntly rounded angle or tooth and posteroventrally with a long, posteriorly directed spur. Dorsum of petiole in profile low, only shallowly convex (text-fig. 5) (Borneo, Sumatra) . . . . . Cataulacus hispidulus


 * Subpetiolar process a simple rectangular or subrectangular rod of varying size and shape; the posteroventral angle may be acute but is without a projecting long spur. Dorsum of petiole in profile high and strongly convex (Text-fig. 6) . . . . . IO-15

IO-15
return to couplet #IO-14
 * First gastral tergite very strongly and distinctly marginate laterally throughout its length, the dorsum markedly separated from the lateral portions of the sclerite. In dorsolateral view the marginations appear as strong as ridges. (China: Hainan Islands) . . . . . Cataulacus marginatus


 * First gastral tergite not marginate, the dorsum rounding into the lateral portions of the sclerite. In dorsolateral view only an uninterrupted, rounded surface is visible. (Throughout Oriental region, West Malaysia, Borneo, Sumatra, Java) . . . . . Cataulacus granulatus