Aulacopone relicta

Found in forested areas of Azerbijan, this ant remains a phylogenetic and behavioral mystery.

The ponerine ant genus Aulacopone, and its only known species A. relicta, were described by Arnoldi (1930) from a unique dealate female collected at Alazapin, near Lenkoran (38° 45'N., 48° 50'E.), in Azerbaydzhan S.S.R., near its border with Iran. The specimen was taken in galleries of the formicine ant Lasius emarginatus, under the bark of an oak stump, in Talisch mid-montane forest. The holotype, which I have not seen, is reportedly in the collection of the Zoological Institute, Leningrad [since Taylor wrote this in 1980 it is known that the type cannot be found and is presumed lost]. A second, previously unreported dealate female of A. relicta, now in the Arnoldi collection at the Institute of Evolutionary Animal Morphology, Moscow, was taken by Arnoldi on Mt. Gugljaband, near Alekseevka, Azerbaydzhan (41° 22 N, 48° 34 E), in 1936 [this specimen has been coated for SEM work]. (Taylor 1980)

Identification
The Aulacopone female is very like her counterparts in species of the Heteroponera imbellis complex, in size, general habitus, structure of the mesosoma, and colour. Aulacopone and Heteroponera share several major features distinguishing them from Gnamptogenys, including the presence of a median longitudinal costa, distinct from other sculpture, on the head (terminating in front of the anterior ocellus in females), and the absence of a tooth or spine on the upper surface of each posterior coxa (a feature of almost all Gnamptogenys species, found nowhere else among the Ectatommini). Aulacopone also shares with Heteroponera those features distinguishing the latter from the neotropical genus Acanthoponera; these include the absence of long propodeal spines and a strong tooth or spine on the petiolar summit, and the lack of a prominent basal lobe accompanying a distinct submedian tooth on each tarsal claw. Basal lobes are characteristic of Acanthoponera. Submedian teeth are vestigially represented on the claws of some neotropical Heteroponera species, though they are lacking from all Australian species, and from Aulacopone. The lack of submedian teeth on the tarsal claws also distinguishes Aulacopone and Heteroponera from the prominent and diverse Australia-based genus Rhytidoponera, the species of which, in addition, almost all have a strong tooth-like process on each lateral pro notal margin. Such structures are lacking in other ectatommine genera, including Aulacopone, and all Heteroponera species except H. relicta (Wheeler). The latter could stand close to the Rhytidoponera ancestry.

The structural features of Aulacopone are, of course, known only for the female; those of the worker must be surmised. A. relicta nonetheless shows clear cryptobiotic tendencies. The female is of small to medium size for an ectatommine, with fine sculpture comparable to that of various Proceratium and Discothyrea species, and relatively pale yellowish brown colour. The pilosity is dense, though short and not unlike that of some Discothyrea species, and the eyes are smaller than would be expected in an epigaeic ectatommine. The really distinctive features of the genus have to do with its cephalic structure, in which the fronto-clypeal part of the head is extended forwards to form a strong triangular process, partly covering the closed mandibles. The antennal fossae are carried forwards on this process almost to the level of the mandibular bases. The resulting structure is, however, very different from that of any Proceratium or Discothyrea species, for here the lobes of the frontal carinae are not elevated; they are instead extended laterally and posteriorly to form, on each side, the upper enclosure of a strong, deep scrobe, in which the folded antenna can be stowed. Such strong antennal scrobes are unusual in ectatommine ants, though those of Heteroponera relicta and of some Discothyrea species are almost as well developed. Each frontal carina is narrowed immediately above the appropriate antennal socket. This might facilitate anterior extension of the scapes, as is so generously accommodated in Proceratium and Discothyrea. Immediately behind this section the carina is laterally expanded and partly reflexed, to form an obtuse lobe, which appears to partially lock the scape into position when the antennae are folded (Arnoldi). These modifications cause the frons and posterior parts of the clypeus to form a regularly convex, more-or-less triangular shield-like face to the cranium, a configuration not unlike that of other small cryptobiotic ants, such as some in the myrmicine tribes Dacetini and Basicerotini. The fronto-clypeal structure of Aulacopone is unlike that of any other ponerine ant, and thus immediately diagnoses the genus. The extent to which it might be associated with specialised trophic behaviour, like egg-feeding, is quite unknown. In addition the petiolar node, though relatively broad, is structured similarly to those of some Discothyrea females, and is quite unlike those of any Heteroponera species. The structure is somewhat like that typical of the primitive ponerine tribe Amblyoponini, and might represent a holdover from a remote amblyoponine ancestry. Abdominal segment IV is somewhat reflexed (Arnoldi), though less strongly so than in Proceratium, Bradoponera or Discothyrea; or even some Heteroponera species (notably Heteroponera leae (Wheeler), in which segment IV is more strongly reflexed than in A. relicta and relatively short compared to segment III). Other descriptive details are covered by Arnoldi. Several points deserve further discussion. (1) The eyes are notably hairy. This might not be the case in workers. However, the only similar condition I have seen in tribe Ectatommini is that of a worker of an undescribed species of Heteroponera (aff. H. leae) from southwestern Western Australia. No other Australian Heteroponera has hairy eyes. (2) The scanning electron microscope has revealed an unusual structure on each pro notal humerus of the subject specimen. Each consists of a small shallow depression, without pilosity, enclosing several irregular troughs which each contain a number of minute pores. These are presumably the ducts of some previously unreported prothoracic gland. A detailed survey by steroscopic light microscope has revealed no comparable structure in any other of the several hundred ectatommine species, of all known genera, represented in the Australian National Insect Collection.

Distribution based on Regional Taxon Lists
Palaearctic Region: Azerbaijan.

Biology
This ant has been collected in only two locations in eastern Azerbijan, in the south in 1930 and in the north in 1936.

Taylor (1980) - Aulacopone thus emerges as a genus close to Heteroponera which, like Proceratium and the Bradoponera Discothyrea line, shows adaptations to a cryptobiotic lifestyle, though these have probably been separately, and convergently evolved in the three lineages. The full degree of cryptobiotic specialisation cannot be assessed until workers of Aulacopone are collected, and checked for fronto-clypeal structure, palpal formula, mesosomal ankylosis, and relative development of the eyes, pilosity and gastral reflexion. The genus can reasonably be considered an ancient ectatommine relict, very restricted in distribution, and perhaps more readily analagous to the extinct Baltic Amber and Florissant ectatommines than to extant species.

Castes
Known only from dealate queens.

Nomenclature

 *  relicta. Aulacopone relicta Arnol'di, 1930a: 140, figs. 1-5 (q.) AZERBAIJAN. [Also described as new by Arnol'di, 1930d: 159.] See also: Brown, 1958g: 206; Taylor, 1980c: 353.

Queen
Taylor (1980) - The measurements (mm) of the Mt Gugljaband specimen are: aggregate total length 4.25; maximum head length 1.08; head width across eyes 1.02; chord length of scape 0.59; maximum diameter of eye 0.24; Weber's length of mesosoma 1.36; scutum width 0.82; petiole width 0.52; petiole height 0.58; width of postpetiole (abd. 11) 0.96.