Terataner

Bolton, B., 1981, A revision of six minor genera of Myrmicinae (Hymenoptera: Formicidae) in the Ethiopian zoogeographical region., Bulletin of the British Museum (Natural History) Entomology 43, pp. 245-307 : 288-290

TERATANER Emery

(Figs 38 - 55)

Terataner Emery, 1912: 103. Type-species: Atopomyrmex foreli Emery , 1900: 274; by original designation. Tranetera Arnold, 1952: 130 [as subgenus of Terataner ]. Type-species: Atopomyrmex bottegoi Emery , 1896: 155; by original designation. Syn. n.

Diagnosis of worker. Monomorphic arboreal myrmicine ants. Mandibles armed with 5 or 6 teeth. Palp formula 5, 3 ( alluaudi ) or 4, 3 ( bottegoi , elegans , luteus , piceus , scotti ). Anterior clypeal margin with a median notch or impression. Median portion of clypeus broad and broadly inserted between the frontal lobes, bounded laterally by a pair of widely separated carinae which run to the anterior margin; lateral portions of clypeus unmodified. Frontal lobes narrow, continuing back into a pair of more or less straight frontal carinae which are usually roughly parallel and relatively close together on the dorsum of the head. Towards the occiput the frontal carinae either fade out or are sharply angled outwards as a ridge or row of tubercles which runs to the sides of the head. Antennal scrobes absent or at most the sides of the head below the frontal carinae with a broad and very shallow concavity. Antennae 12 - segmented with a 3 - segmented club, the scapes when laid back failing to reach the occipital margin. Eyes large and conspicuous, situated at or in front of the midlength of the head. Occipital corners tuberculate or denticulate in full-face view. Pronotum marginate laterally and usually also anteriorly, the lateral marginations generally simple but sometimes expanded into ornate lobes or flanges. Pronotal shoulders angulate, denticulate or tuberculate in dorsal view. Promesonotal suture absent on the dorsum or represented by a line or slight indentation, only rarely easily visible. Mesonotum usually marginate laterally and forming a low projecting angle or tubercle in dorsal view; rarely immarginate and armed with a sharp denticle laterally. Metanotal groove impressed, most frequently only shallowly so but deep in some species; very shallow indeed in some samples oi elegans . Propodeum bluntly marginate to rounded laterally, unarmed or with a pair of denticles or teeth. Metapleural lobes large and strongly developed; ventral margin of metapleuron with a strong broad groove running forward from the orifice of the metapleural glands. Ventral surface of alitrunk between hind coxae entire, simple, without a broad deep circular pit. Middle and hind tibiae frequently with a distinct simple spur, the spur reduced in some and indistinguishable from the hairs of the tibial apex in others. Petiole with a short, stout anterior peduncle, the node narrow and tapering dorsally so that it appears triangular or conical in profile. In anterior or posterior view the narrow dorsum of the node either forms a transverse crest or is indented medially so that a pair of blunt prominences are formed laterally. In some these prominences are acute and dentiform, in others developed into quite long teeth; rarely the petiole is strongly bispinose.

In one species ( scotti ) the petiole is developed into a very high plate dorsally which has a central emargination. Postpetiole simple or armed dorsally with a transverse crest or a single spine. Pilosity very variable, some species densely hairy, others almost hairless. Sculpture generally of coarse rugae or sulci, but reduced in the African species piceus , elegans , luteus and velatus .

Terataner is a small genus of arboreal ants containing 12 species, six of which occur in the Ethiopian region and six in the Malagasy region. Nests are constructed in rotten parts of standing timber, often some considerable distance above the ground. Of the African species four occur quite widely in West and Central African forests { luteus , elegans , piceus , velatus ), one is East African ( bottegoi ) and the last ( transvaalensis ) is known only from South Africa. The first four named form a complex of closely related species; the last two form a close species-pair which shows marked similarity to the Malagasy species foreli , rufipes , steinheili and xaltus . Apart from these Madagascar has another species, alluaudi , which is certainly the most bizarre representative of the genus as it is presently understood. The final species of the Malagasy region, scotti , is known only from a single worker from the Seychelles. A synopsis of the Malagasy species is given at the end of this section.

Females (queens) are known for a few species and in general show the same characters as the workers, except for the usual modifications associated with this caste. Males are very poorly known, having been recorded only for elegans , scotti and foreli , the total number of specimens amounting to six or seven.

Arnold (1952) proposed a subgenus of Terataner which he called Tranetera , erected to include only the species bottegoi and transvaalensis , with the former nominated as type-species. In the same paper he chose to treat Atopula Emery as a subgenus of Terataner . It has since been shown (Bolton, 1976; 1980) that the type-species of Atopula , A. nodifera (Emery), is in fact a tetramoriine, and the name Atopula has fallen as a straight synonym of Tetramorium Mayr.

Turning now to Tranetera , it seems probable that Arnold erected this name on the strength of original descriptions alone, and did not see any material other than that of transvaalensis which, however, he did recognize as being close to bottegoi . From his description of the subgenus only three characters emerge to differentiate Tranetera from Terataner , namely that in Tranetera the promesonotal suture was clearly defined, the metanotal groove (= meso-epinotal suture) was not depressed, and that the petiole was quadrate and without spines. Opposed to this the six species which he left in Terataner ( alluaudi , foreli , luteus , rufipes , scotti and steinheili ; piceus is not mentioned and the description of elegans had not then appeared) were supposed to have the promesonotal suture obsolete or slightly indented at the sides, the metanotal groove deeply depressed and the petiole not quadrate, armed with two long spines.

Taking the last character, it is obvious when specimens are compared that an almost complete morphocline is present. Only one species has the petiole transverse above, transvaalensis , and even here a feeble indentation can be seen; only one species, alluaudi , has the petiole strongly bispinose. Between these two extremes the petiole dorsally is indented to emarginate in bottegoi , bilobate in scotti , shortly and bluntly bidentate in luteus , long bidentate in steinheili . The presumed separation petiole not quadrate and with two long spines versus petiole quadrate and without spines, does not exist in fact; all major steps between them being bridged in already described species.

Similarly with the degree of definition of the promesonotal suture. It is quite clearly marked in transvaalensis (though fused), weakly defined in bottegoi , vestigial in scotti where it is indicated more by a change in sculpture pattern, almost invisible in steinheili where at certain angles the strong sulcate sculpture is very feebly indented along the former track of the suture; obliterated elsewhere. It should be noted that all species have an impression, notch or groove at each side of the dorsum where pronotum and mesonotum meet, which indicates the ends of the former track of the promesonotal suture, and which separates the marginations of the two segments.

Finally, the degree of impression of the metanotal groove varies considerably from species to species. The variation does not allow a split such as that proposed by Arnold and a number of species were incorrectly placed by him, as in bottegoi the metanotal groove is impressed where it is as shallow in luteus as it is in transvaalensis .

Thus the concept of a subgenus Tranetera collapses and the name is relegated to the synonymy. In point of fact Terataner , as presently constituted, forms a fairly compact genus, within which the following species-complexes can be discerned.

luteus-complex ( elegans , luteus , piceus , velatus ). Frontal carinae more or less straight, fading out posteriorly, not angled outwards towards the sides of the head. Sculpture fine. Hairs very sparse and scattered or absent on first gastral tergite. Dorsal (outer) surfaces of middle and hind tibiae without projecting hairs. West and Central Africa.

foreli-complex ( bottegoi , foreli , rufipes , scotti , steinheili , transvaalensis , xaltus ). Frontal carinae angled outwards posteriorly, running across the head either to the sides or towards the occipital corners as a crest, ridge or row of tubercles. Sculpture coarse. Hairs dense and very conspicuous on first gastral tergite. Dorsal (outer) surfaces of middle and hind tibiae with projecting hairs. East and South Africa, Madagascar, Seychelles.

alluaudi-complex ( alluaudi ). As foreli-complex but frontal carinae feeble, sometimes almost indistinguishable from the cephalic sculpture, not running transversely on the head posteriorly. Postpetiole with a single long median dorsal spine. Margins of pronotum expanded into a pair of broad laminae. Madagascar.

Terataner belongs to a group of genera which also includes the African genus Atopomyrmex Andre , the Oriental / Indo-Australian genus Dilobocondyla Santschi and the predominantly Australian genera Dacryon Forel, Peronomyrmex Viehmeyer , Podomyrma F. Smith and Pseudopodomyrma Crawley (Taylor, 1970). Possibly also the strange monotypic genus Ireneopone Donisthorpe of Mauritius belongs to this assemblage. As can be seen, the only other African genus noted is Atopomyrmex ; the two are separated as follows in the worker.