Ectomomyrmex Mayr

Schmidt, C. A. & Shattuck, S. O., 2014, The Higher Classification of the Ant Subfamily Ponerinae (Hymenoptera: Formicidae), with a Review of Ponerine Ecology and Behavior, Zootaxa 3817 (1), pp. 1-242 : 191-193

Ectomomyrmex Mayr

Fig. 44

Ectomomyrmex Mayr, 1867: 83 (as genus). Type-species: Ectomomyrmex javanus Mayr, 1867: 84 ; by subsequent designation of Bingham, 1903: 85. Gen. rev.

Ectomyrmex Donisthorpe, 1943b: 641 (incorrect subsequent spelling of Ectomomyrmex ).

Ectomomyrmex is a medium-sized genus (27 described species) restricted to Asia and Australia. They are apparently epigeic generalist predators.

Diagnosis. Ectomomyrmex workers can be identified by the following combination of characters: head, mesosoma and petiole strongly sculptured, head usually prismatic posteriorly, mesopleuron divided by a transverse groove, and petiole with a sweeping posterior face. Ectomomyrmex workers are similar to those of some Ponera species (e.g., P. alpha ), but Ectomomyrmex workers lack an anterior fenestra in the subpetiolar process and have two metatibial spurs and a divided mesopleuron. Ectomomyrmex is also superficially similar to Pachycondyla , but Ectomomyrmex lacks the complex metapleural gland orifice and hypopygial spines of Pachycondyla , and Pachycondyla lacks the prismatic head shape of Ectomomyrmex . Ectomomyrmex is also somewhat similar to Cryptopone and Pseudoponera , but differs from them in having strong sculpturing, larger eyes, no basal mandibular pit, a prismatic head, divided mesopleuron, slit-shaped propodeal spiracles, a sweeping posterior petiolar face, and no traction setae on the mesotibiae. Ectomomyrmex may be confused with Pseudoneoponera or Bothroponera , but Ectomomyrmex lacks the shaggy pilosity and longitudinally striate tergite A3 of Pseudoneoponera , and the large eyes, undivided mesopleuron, and block-like petiole of Bothroponera .

Synoptic description. Worker. Medium to large (TL 5–12.8 mm) ants with the standard characters of Ponerini . Mandibles triangular, with up to 10 teeth on the masticatory margin and often a faint basal groove. Anterior clypeal margin convex, sometimes medially emarginate. Frontal lobes small to moderate in size. Eyes very small to small, located anterior of head midline. Head usually prismatic posteriorly, with distinct angular ridges between dorsal and lateral surfaces. Mesopleuron divided by a transverse groove. Metanotal groove obsolete or reduced to a simple suture. Propodeum broad to narrowed dorsally, with sharp posterior margins. Propodeal spiracles slitshaped. Metapleural gland orifice sometimes with a posterior flange. Metatibial spur formula (1s, 1p). Petiole squamiform to nodiform, the scale usually much wider than long, in dorsal view with a convex anterior face and in lateral view a forward-sweeping posterior face. Gaster with a moderate girdling constriction between pre- and postsclerites of A4. Head, mesosoma and petiole deeply striate, rugoreticulate or punctate, the gaster usually finely punctate but sometimes striate (e.g. in E. acutus ). Head and body with abundant short pilosity and light to dense pubescence. Color black.

Queen. Similar to worker but slightly larger, winged, with ocelli, larger compound eyes, and the usual modifications of the thoracic sclerites ( Ogata, 1987).

Male. See description by Ogata (1987).

Larva. Not described.

Geographic distribution. Ectomomyrmex ranges across most of the Indo-Australian and Australasian regions, from India east to Japan and from northwestern China south to northern Australia ( Brown, 1963).

Ecology and behavior. Very little is known about the habits of Ectomomyrmex . Anecdotal observations, and the moderately small eyes of Ectomomyrmex workers, suggest that their foraging habits are somewhat intermediate between epigeic and hypogeic. They are apparently generalist arthropod predators ( Wilson, 1958c, 1959a), and Ke et al. (2008) observed that workers of E. astutus were particularly fierce predators of termites in an artificial arena. Wilson (1958c) observed E. aciculatus foraging diurnally on the forest floor among and under leaf litter, observed E. exaratus foraging on the forest floor, and reported that E. striatulus forms small colonies (fewer than 100 workers) and nests in rotting logs. Like its close relatives Ponera and Cryptopone , workers of Ectomomyrmex apparently feign death when disturbed ( Wilson, 1958c).

Phylogenetic and taxonomic considerations. Ectomomyrmex was described by Mayr (1867) to hold the species E. javanus and E. sundaicus (now a junior synonym of E. javanus ). Mayr did not designate a type species, but Bingham later (1903) designated E. javanus the type species. Subsequent to its original description, Ectomomyrmex was variously treated as a distinct genus (e.g., Dalla Torre, 1893; Brown, 1963; Ogata, 1987), as a subgenus of Pachycondyla (e.g., Emery, 1901; Wheeler, 1910; Forel, 1917), and eventually as a junior synonym of Pachycondyla ( Brown, 1973, and most subsequent authors; but see Ogata, 1987).

Molecular evidence gives strong support for a sister relationship between Ectomomyrmex and Ponera , and not between Ectomomyrmex and Pachycondyla ( Schmidt, 2013) . A close relationship between Ectomomyrmex and Ponera is also supported by morphology ( Taylor, 1967). P. alpha in particular is quite similar to Ectomomyrmex , and it is possible that these genera are not reciprocally monophyletic.

Figures

FIGURE 44. Worker caste of Ectomomyrmex ruficornis: lateral and dorsal view of body and full-face view of head (CASENT0172434, April Nobile and www.antweb.org); world distribution of Ectomomyrmex.