Cataulacus species groups

Ethiopian and Malagasy Regions

Thirty-four species (more post 1974, which is when this was written) are known from the Ethiopian and Malagasy regions, of which 7 are peculiar to Madagascar and its island systems. A single species is found on Madagascar which is also known from southern Africa but otherwise the Malagasy fauna is quite distinctive.

The study of the species of these regions is by necessity based upon the worker caste as the sexual forms remain unknown in a majority of cases.

The species fall into four groups which are listed below, along with their synonyms. Characterizations of the groups are given under the appropriate sections. Previous notes on the biology of the Ethiopian regional fauna are to be found in Arnold (1917) and Wheeler (1922a), and the species known at that time were catalogued by Wheeler (1922c). References to nest sites, etc., are scattered through the literature of original descriptions; these have been noted in the systematic treatment by species.

Unsurprisingly 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.

huberi group

Small to very large species (TL 4.0 – 11.0 approx.) in which the head is always short and broad, and always broader than long (CI > 111), with a measured range of CI 101-132. The eyes are relatively small or very small, usually with OI < 30, but in regularis and in some individuals of egenus they may be larger, up to OI 35.

The dorsum of the head capsule behind the clypeus and the dorsal alitrunk are completely devoid of hairs except in porcatus where a few short, clavate hairs are present on the latter. Marginal hairs, projecting laterally are common amongst the species on the head and alitrunk. The pronotum is marginate laterally, often strongly so, more rarely the margination is reduced (oberthueri) but in no case is it denticulate; although in some species the margin is produced into one or two distinct teeth. Propodeal spines are usually long, stout and acute, but one species lacks such spines (inermis). Sculpturation throughout the group is predominantly of a fine and dense reticulate-puncturation with an overlying very weak rugulation or a rugoreticulum. Exceptions are known and in the case of regularis and its immediate allies a marked longitudinal sulcation is developed.

In some species of the group large workers are developed which may, if taken singly, appear to belong to separate species as they tend to differ from more usual-sized individuals in details of structure and sculpturation. Some of the synonymy in the group is based upon the description of single specimens of such species, where usually the larger individual is given one name and the smaller another name, for example coriaceus and pullus; tardus and schoutedeni. When good series have been acquired the differences between such large and small forms have been nullified.

A number of closely related species pairs occur within the group. For instance lobatus and inermis share the same development of the postpetiole, with a dorsal longitudinal groove dividing the segment; egenus and huberi have the same form of petiolar and gastral development; and regularis and porcatus have longitudinal sulci as their basic sculpturation. The group contains 12 species, of which 4 are peculiar to the Malagasy region. The species are distributed through the forest zones of the two regions, usually in the rain forests of West and Central Africa and eastern Madagascar but also in areas of drier forest.

tenuis group

Small to minute species, TL usually less than 4.0, rarely slightly more; measured range TL 2.7 – 4.4, the latter occurring only in large workers of elongatus. Slender, narrowly built forms with HW <1.0, often <0.90 and with PW <0.80. The head is always longer than broad, CI <100 and in most cases less than 95. Eyes relatively large or enormous, OI usually > 50, always 49 or more except in elongatus where one worker measured had OI 45.

Hairs are invariably present on the dorsal surfaces of the head, body and appendages. These hairs are usually short, stout and simple but in some species they are variously modified; for instance at least the cephalic hairs may be clavate (brevisetosus, vorticus), or long and sinuate (elongatus), or short, simple and very strongly adpressed (adpressus). The pronotum is marginate laterally, the sides usually almost parallel, and in most species the margins are serially denticulate. The propodeal spines are usually short and acute, not uncommonly somewhat dorsoventrally flattened. Sculpturation in the group is basically of a rugoreticulum with reticulate-punctate interspaces, but numerous species have longitudinal rugulation or sulcation, at least in part.

This group of ten species includes all the small, narrowly-built, large-eyed forms with elongate heads. They are very closely related to the intrudens group, from which they may eventually be found to be inseparable.

The common species pygmaeus apparently forms a link between the two groups but on weighing the characters which it possesses it falls in with intrudens rather than with the relatives of tenuis. However, as it resembles the members of the present group so closely and as one of the species included in this group was originally described as an infraspecific form of pygmaeus, separatory notes and comments are included under some of the species.

The majority of species in the present group are forest-dwelling forms but brevisetosus seems able to survive in any area of Africa in which conditions are not too inimical. Only a single species of the group, tenuis itself, is found in Madagascar.

intrudens group

Small to medium-sized species, TL usually more than 4.0, rarely slightly less, the measured range of TL 3.5 – 6.1, the lower measurements occurring only in fricatidorsus and small pygmaeus workers. Usually rather stoutly built forms with HW > 1.00, rarely less and never less than 0.90; PW > 0.80, very rarely slightly less. The head is most commonly broader than long, CI > 100; in twq species CI straddles 100 but only in pygmaeus and ebrardi is it consistently less than 100. Eyes relatively small, or < 50 in all cases, usually less than 46, with a measured range of or 34 - 46.

Hairs always present on the dorsal surfaces of the head, body and appendages, usually conspicuous, short, stout and simple but in some species reduced in size, short and inconspicuous. Pronotum marginate laterally, the margins armed with a series of denticles or small teeth. Sides of pronotum usually somewhat convex in dorsal view and the alitrunk usually strongly narrowed behind the pronotum. Propodeal spines moderate in size, reduced to mere teeth in mocquerysi, often quite strongly dorsoventrally flattened and broad in dorsal view. Sculpturation is basically a rugoreticulum with reticulate-punctate interspaces, but this is reduced in some species.

Of the nine species included in this group two are restricted to the Malagasy region. Of the remainder the majority of species are savannah or veldt inhabiting and form the major part of the cataulacine fauna of southern and eastern Africa. One species, pygmaeus, seems equally able to survive in most areas but it shows a preference for savannah-like vegetation. The only rain forest inhabiting species of this group which has not been found outside such areas is mocquerysi, and it is interesting to note that this species is also structurally the most aberrant of the group, with a highly modified pedicellar structure.

guineensis group

Medium to large-sized species, TL 4.5 – 9.5, with the head always broader than long, often considerably so, CI 101 - 121, and with relatively small to medium eyes, OI < 45 (measured range of OI 26 - 43).

Simple stout hairs numerous upon all dorsal surfaces of the head, body and appendages except in some individuals of guineensis where they may be reduced in number. Pronotum marginate laterally, often strongly so, the margins armed with a series of small teeth or denticles. Besides this the posterolateral portion of the pronotal margination is expanded, usually strongly so, and projects as a spine, tooth or plate. Propodeal spines long, stout and acute, not dorsoventrally flattened.

The three species included in this small group inhabit the rain forests of West and Central Africa, and guineensis is probably the most common species of the genus in such areas.

Indo Australian and Oriental Regions

In all, some 17 species of Cataulacus have been recorded from the Indo-Australian and Oriental regions, one species of which (longinodus) is known only from the female caste. Of the 16 species in which the worker is known, females are known for ten of them and males are known for nine. The association of some isolated males and females in the present study has been tentative and where this is the case the description under the individual species headings has been quoted as 'putative male', etc.

The worker caste the species fall into three informal groups.

What little is known of the biology of the species is mostly to be found in the publications of Wroughton (1892) and Bingham (1903). Details of the biology are included under the individual species headings, but it is probably safe to say that the biologies of the species do not differ markedly from those of species of the Ethiopian region, which are rather better documented in some cases.

The species are rather thinly distributed, and as one moves eastwards through the island systems and towards New Guinea the number of recorded species gradually falls off, as it also does along the Sumatra-Timor island chain. These may be illustrated by the following west-east island series and the number of species noted from each:

West Malaysia 7, Borneo 6, Philippines 3, Sulawesi 1, Waigeo 1, New Guinea 0; and similarly: Sumatra 6, Java 2, Sumbawa 0.

granulatus group

The group contains eight species characterized by their abundance of conspicuous short, erect, stout and blunt hairs upon all dorsal surfaces of the head and body and by the coarse nature of the sculpturation which in most cases is a rugoreticulum upon the head and dorsal alitrunk. The reticulae are often raised into minute peaks or tubercles at their points of intersection. The interspaces of the rugoreticulum are usually finely and densely reticulate-punctate, but in some species the puncturation is reduced and the interspaces are dully shining. Denticulation of the margins of the head and alitrunk is always well developed and all members of the group present a very rough, pilose aspect.

In the majority of species the propodeal spines are short or very short, and widely separated basally, but in setosus and nenassus they are elongate and divergent. It is interesting to note the presence of very short, strongly clavate or subglobular hairs in simoni, the smallest species of the regional fauna, as this character compares well to similar developments in some of the smaller species of the Ethiopian region. The possible advantages of hairs of this nature are unknown, but some populations of granulatus, the most widespread species of the group, develop hairs which are very similar.

Six of the eight species belong to two complexes of closely related species. The first and largest complex, centring on granulatus itself also includes marginatus, hispidulus and muticus in which the occipital crest tends to be incomplete or broken medially and the propodeal spines are short and very widely separated basally. The second complex includes setosus, nenassus and most probably longinodus, the worker of which is not known. In these species the occipital crest is complete and strongly developed, armed with denticles throughout its length, and the propodeal spines are long and strong, paralleling the condition usual in the taprobanae group.

The majority of the species are distributed to the west of the 120th meridian of easterly longitude, which runs roughly through the islands of Luzon, Sulawesi and Flores; only a single species, setosus, is found to the east of that line. At present the greatest number of species of the group are found on Java, but this picture will probably change as collections from other localities become larger.

taprobanae group

The species of the taprobanae group appear to have developed from a long-spined granulatus-like stock by the reduction of sculpture and reduction or complete loss of erect hairs from the dorsal surfaces of the body, particularly the head and alitrunk. The link between the two groups appears to be through setosus and taprobanae. In the last named species hairs are still relatively distinct, but in the closely allied flagitiosus they are very much reduced both in size and number. In latus some minute, flattened hairs may be present dorsally but in all other species they are completely lacking. Sculpturation is principally a fine, dense reticulate-puncturation which usually overlies any rugosity which may be present. A tendency of many species of the group is to replace the reticulate-rugulation of the mesonotum and propodeum by a regular series of low, longitudinal rugae which are more or less parallel. This is accomplished by the reduction or loss of the cross-meshes of the reticulum. In cases where this has occurred the resultant longitudinal rugae are very low and broad and their surfaces are covered by a dense reticulate-puncturation. Propodeal spines in all the species are well developed and relatively long and broad.

In the majority of species the occipital crest is well developed, although often not armed with denticles. The reduction in size and number of denticles on the crest and margins of the alitrunk appears to be correlated with the loss of erect hairs and reduction of the coarseness of the sculpturation in many species. Some species, especially those closest related to reticulatus, have the median portion of the occipital crest produced into a rectangular ridge which is quite distinct in full-face view.

The distribution of the group extends eastwards from India to the Philippines and to Sulawesi. No species seem to be present east of these islands and, strangely, the group is not known from Java and is but poorly represented on Sumatra. The greatest number of species are found on Borneo, in the territories of East Malaysia.

insularis group

The single species assigned to this group, insularis is a junior synonym of Cataulacus horridus.

Bolton characterized this group as follows: "The single species placed in this group .... is characterized by a lack of margination on the alitrunk, great development of occipital and propodeal spines and the extreme coarseness of the sulpturation, especially on the alitrunk. Whilst the hairyness of the species and the form of sculpture suggest affinities with the granulatus group some characters are present which are reminiscent of the guineensis group of species from the Ethiopian region, namely the large size, strong occipital and propodeal spines and the pronounced tubercle on the alitrunk, in the same position as the spine of guineensis."