Plectroctena
Creators: name: Wheeler, W. M.
Publisher: name: Zenodo
Year: 1922
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hymenoptera
Formicidae
Plectroctena

description: Plectroctena F. Smith
Large or medium-sized black or castaneous ants, with shining surface, sparsely punctate.
Worker monomorphic, with large, rectangular and rather flat head, with small, flat, anteriorly situated eyes. Clypeus very short, its anterior border straight in the middle, emarginate on each side at the mandibular insertion, apparently not extending back between the frontal carinae, the latter overhanging the clypeus and forming with the front an elevated lobe, longitudinally sulcate in the middle. Mandibles long, linear, feebly curved, with a deep narrow furrow running nearly their full length on the dorsal surface, their tips blunt, the inner margin armed with a strong tooth at the basal third and another obtuse tooth, sometimes indistinct, between the latter and the tip. Antennae 12-jointed, the funiculi somewhat thickened towards their tips, the first joint shorter than the second. Thorax large and depressed, premesonotal suture distinct, mesoepinotal suture obsolete, epinotal declivity marginate on the sides. Petiole with a laterally compressed node, with the anterior and posterior surfaces vertical in profile, the dorsal surface horizontal. Constriction between the postpetiole and gaster pronounced, with well-developed stridulatory surface. Gaster short, formed largely by the first segment. Median spurs of middle and hind tibiae large and pectinated, lateral spurs lacking.
Female winged, apterous or ergatomorphic, larger than the worker but otherwise similar. Eyes and ocelli small. Anterior wings with a discoidal cell, two cubital cells and the radial cell closed.
Male about the size of the worker. Frontal carinae short, erect, closely approximated, bringing the insertions of the antennae close together. Antennal funiculi filiform, their first joint very short; scapes stout, shorter than the second funicular joint. Mandibles small, linear, parallel-sided, edentate, with rounded tips. Mesonotum with distinct Mayrian furrows; scutellum longitudinally grooved in the middle. Genitalia retracted; pygidium terminating in a blunt or truncated point. Wings short.
This singular genus is confined to the Ethiopian Region (Map 13). Arnold has observed the habits of the type species, P. mandibularis, in South Africa. "The entrances to the nest are generally indicated by large heaps of earth. The chambers are placed deep below the surface, seldom less than 2 feet, and the number of individuals seldom exceeds 50. It is a sluggish and timid ant, the workers foraging singly. The food includes termites, but consists chiefly of millipeds and beetles." Another South African species described by Arnold as P. subterranea is castaneous red, measures only 7.5 to 10 mm., and has exceedingly small eyes. It, in all probability, belongs to a different genus. In the generic key it runs down to Myopias and is provisionally referred to that genus.
The character of the females in the four described species of Plectroctena has not been adequately ascertained. Winged females of P. minor and subterranea are known, but no winged females of mandibularis. According to Arnold, this species has ergatoid females differing "from the worker chiefly in size, but the head and abdomen are proportionally wider and longer. The longitudinal impression on the pronotum is shallower, while that of the dorsum of the epinotum is deeper and wider. In a nest of three dozen or so individuals, not more than two or three of these forms are to be found, and usually only one." It seems that Forel saw one of these ergatoid females and described it as a subspecies (major) of mandibularis. There is, however, still another type of female, at least in P. minor, of which I describe a specimen below, with ocelli and slightly larger eyes than the worker and with the thorax essentially like that of the winged female, but without the slightest indications of ever having borne wings.
description: Published as part of Wheeler, W. M., 1922, The ants collected by the American Museum Congo Expedition., pp. 39-269 in Bulletin of the American Museum of Natural History 45 on pages 85-87