Procerapachys Wheeler, W. M. 1915b

Borowiec, Marek L., 2016, Generic revision of the ant subfamily Dorylinae (Hymenoptera, Formicidae), ZooKeys 608, pp. 1-280 : 163-166

Taxon classification Animalia Hymenoptera Formicidae

Procerapachys Wheeler, W. M. 1915b

Type-species.

Procerapachys annosus , by original designation.

Procerapachys is an extinct genus known from Baltic amber.

Diagnosis.

Worker. The extinct Procerapachys is apparently unique among non-army ant dorylines in having a large but unarmed pygidium. All other dorylines with unarmed pygidium have either highly positioned propodeal spiracles and no propodeal lobes ( Aenictus , Aenictogiton , Dorylus ) or a reduced pygidium ( Leptanilloides ). When pygidium is not clearly visible, these often heavily-sculptured ants can be confused with Chrysapace , which also occurs in Eocene ambers (see under that taxon above). Chrysapace and Procerapachys differ in spur formula, however. The former has two pectinate spurs on each mid and hind tibia, and the latter has only one pectinate spur. Procerapachys specimens were also reported to have palp formula 5,4, which is different from 5,3 counted in one of the extant Chrysapace .

Male. The status of the putative males of Procerapachys is uncertain, but the specimens originally attributed to this genus had well-developed wing venation with two submarginal cells and the marginal cell closed, similar to Chrysapace and Cylindromyrmex . The most reliable character that separates these males from these two genera is a single pectinate tibial spur in Procerapachys and two spurs present in both Chrysapace and Cylindromyrmex .

Description.

Worker.Head: Antennae with 12 segments. Apical antennal segment not enlarged, not broader and longer than two preceding segments combined. Clypeal apron unknown. Lateroclypeal teeth unknown. Parafrontal ridges reduced. Torulo-posttorular complex vertical. Antennal scrobes absent. Labrum shape unknown. Proximal face of stipes unknown. Maxillary palps 5-segmented. Labial palps 4-segmented. Mandibles triangular, edentate. Eyes present, composed of more than 20 ommatidia. Ocelli absent or present. Head capsule with differentiated vertical posterior surface above occipital foramen. Ventrolateral margins of head unknown. Posterior head corners dorsolaterally immarginate. Carina surrounding occipital foramen unknown. Mesosoma: Pronotal flange separated from collar by distinct ridge. Promesonotal connection with Pronotomesopleural suture conspicuous and complete, but immobile. Pronotomesopleural suture complete, continuous with promesonotal Pronotomesopleural suture. Mesometapleural groove not impressed. Transverse groove dividing mesopleuron absent. Pleural endophragmal pit concavity unknown. Mesosoma dorsolaterally immarginate. Metanotal depression or groove on mesosoma absent. Propodeal spiracle situated low on sclerite. Propodeal declivity with distinct dorsal edge or margin and rectangular in posterior view. Metapleural gland unknown. Propodeal lobes present, well developed. Metasoma: Petiole anterodorsally unknown, dorsolaterally immarginate, and laterally above spiracle marginate. Placement of helcium unknown. Prora unknown. Spiracle openings of abdominal segments IV–VI unknown. Abdominal segment III anterodorsally unknown and dorsolaterally unknown. Abdominal segment III more than half size of succeeding segment IV, which is weakly constricted at presegmental portion (uninodal waist). Girdling constriction of segment IV present, i.e. pre- and postsclerites distinct. Cinctus of abdominal segment IV unknown. Abdominal segment IV not conspicuously largest segment. Abdominal tergite IV not folding over sternite, and anterior portions of sternite and tergite equally well visible in lateral view. Girdling constriction between pre- and posttergites of abdominal segments V and VI absent. Girdling constriction between pre- and poststernites of abdominal segments V and VI absent. Pygidium large, with impressed medial field and simple, not armed with cuticular spines or modified setae. Hypopygium unknown. Legs: Mid tibia with single pectinate spur. Hind tibia with single pectinate spur. Hind basitarsus not widening distally, circular in cross-section. Posterior flange of hind coxa unknown. Metatibial gland unknown. Metabasitarsal gland unknown. Hind pretarsal claws unknown. Hind pretarsal claws simple. Polymorphism: Unknown.

Male. (putative, see under Taxonomy and phylogeny below) Head: Antennae with 13 segments. Clypeal lamella unknown. Parafrontal ridges unknown. Torulo-posttorular complex vertical. Maxillary palps unknown. Labial palps unknown. Mandibles triangular, edentate. Ventrolateral margins of head unknown. Carina surrounding occipital foramen unknown. Mesosoma: Pronotal flange separated from collar by distinct ridge. Notauli unknown. Transverse groove dividing mesopleuron absent. Propodeal declivity with distinct dorsal edge or margin. Metapleural gland opening unknown. Propodeal lobes present. Metasoma: Petiole anterodorsally immarginate, dorsolaterally immarginate, and laterally above spiracle unknown. Helcium in relation to tergosternal Pronotomesopleural suture placed at posttergite and axial. Prora unknown. Spiracle openings of abdominal segments IV–VI circular. Abdominal segment III more than half size of succeeding segment IV; latter weakly constricted at presegmental portion (uninodal waist). Girdling constriction of segment IV present, i.e. pre- and postsclerites distinct. Cinctus of abdominal segment IV unknown. Girdling constriction between pre- and postsclerites of abdominal segments V and VI absent. Abdominal segment IV not conspicuously largest segment. Abdominal sternite VII simple. Abdominal sternite IX unknown. Genitalia: Genital morphology unknown. Legs: Mid tibia with single pectinate spur. Hind tibia with single pectinate spur. Posterior flange of hind coxa unknown. Metatibial gland unknown. Metabasitarsal glands unknown. Hind pretarsal claws unknown. Wings: Tegula unknown. Vein C in fore wing present. Pterostigma broad. Abscissa R·f3 present, running toward distal wing margin and enclosing cell with Rs·f5. Abscissae Rs·f2-3 present, connecting with Rs+M&M·f2. Cross-vein 2r-rs present, differentiated from Rs·f4 by presence of Rs·f2-3. Abscissae Rs·f4-5 differentiated into Rs·f4 and Rs·f5 by 2rs-m. Abscissa M·f2 in fore wing present, separated from Rs+M by Rs·f2. Abscissa M·f4 in fore wing present, reaching wing margin. Cross-vein 1m-cu in fore wing present. Cross-vein cu-a in fore wing present, arising from Cu and distal to, at or near M·f1. Vein Cu in fore wing present, with both branches Cu1 and Cu2. Hind wing venation unknown.

Gyne. Not described. Wheeler (1915) mentioned that some of the specimens possessed ocelli while others did not and suggesting that these may represent ergatogynes.

Larva. Not described. Presence of cocoons unknown.

Taxonomy and phylogeny.

Procerapachys was described based on several workers and two male specimens by W. M. Wheeler (1915) in his monograph on the Baltic amber collection of the Geological Institute of Königsberg (now Kaliningrad, Russia). Unfortunately, most of this collection was destroyed during WWII, including the Procerapachys material (Dlussky, 2009). Dlussky (2009) redescribed the genus based on additional specimens of what he identified as the type species, Procerapachys annosus , designated a neotype for it, and added a new species, Procerapachys sulcatus . Both worker and putative male morphologies of Procerapachys annosus and Procerapachys sulcatus are reminiscent of the extant genus Chrysapace . If the published descriptions are accurate, however, there are important differences that include a single pectinate spur on each mid and hind tibiae (mentioned by both Wheeler and Dlussky), different palp formula, and, perhaps most importantly, a pygidium not impressed and without modified spine-like setae in the worker. According to the descriptions it also appears that at least some specimens of Procerapachys lack ocelli, while ocelli are present in all Chrysapace material I examined in the course of this study. In addition, one of the species, Procerapachys favosus , lacks the coarse sulcate sculpturing characteristic of Chrysapace . In fact, there are amber doryline specimens without coarse sculpturing that fit the original Procerapachys by having a single tibial spur and a smooth pygidium, for which I was able to examine high-quality photographs and consult these characters with Vincent Perrichot, who was able to confirm them directly on the specimens. Unfortunately, I was not able to examine any of the specimens on which Dlussky based his descriptions. I have examined a specimen identified as Procerapachys annosus from the collection of Senckenberg Forschungsinstitut und Naturmuseum Frankfurt and found it to be a typical Chrysapace with two conspicuous tibial spurs. I have also examined photographs of a specimen (Vincent Perrichot pers. comm.) from a private collection that fits the original description of Procerapachys annosus and its habitus appears to be distinct from Chrysapace , although I could not assess the shape of the pygidium or tibial spur configuration. Thus at least some of the species attributed in the past to Procerapachys indeed represent a distinct doryline lineage. In the absence of strong evidence to the contrary, I treat Procerapachys as distinct from Chrysapace or any other genus recognized here. However, a careful reevaluation of the amber fossil dorylines, most crucially the neotype of Procerapachys annosus , as well as the putative males, is much needed.

Distribution.

Eocene Baltic and Bitterfeld ambers.

Species of Procerapachys

† Procerapachys annosus Wheeler, W. M. 1915b: Baltic amber

† Procerapachys favosus Wheeler, W. M. 1915b: Baltic amber

† Procerapachys sulcatus Dlussky, 2009: Baltic amber