Pristomyrmex orbiceps

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Pristomyrmex orbiceps
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Crematogastrini
Genus: Pristomyrmex
Species: P. orbiceps
Binomial name
Pristomyrmex orbiceps
(Santschi, 1914)

Pristomyrmex orbiceps casent0417737 profile 1.jpg

Pristomyrmex orbiceps casent0417737 dorsal 1.jpg

Specimen labels

Synonyms

P. orbiceps is a widely distributed species, occurring throughout the wet forest zones of West and Central Africa. Nests are constructed in fallen twigs or larger pieces of wood in the leaf litter layer and workers forage singly in the litter.

Identification

The separation of orbiceps from other African species is straightforward. It differs from Pristomyrmex cribrarius as that species is heavily sculptured and densely hairy. Pristomyrmex trogor lacks frontal carinae, has long scapes and relatively small eyes. The widely distributed Pristomyrmex africanus differs from orbiceps as follows:

orbiceps - Pronotum with a pair of blunt tubercles. Maximum eye diameter 0.18-0.21 x HW. Eye with usually 7-9 ommatidia in the longest row (sometimes with 6). Dorsum of head behind antennal insertions with 2-3 pairs of hairs. Dorsal alitrunk with 1 pair of hairs. Head between frontal carinae smooth. Scapes relatively somewhat shorter, SI range 80-87.

africanus - Pronotum with a pair of acute teeth or short spines. Maximum eye diameter 0.12-0.15 x HW. Eye with only 4-5 ommatidia in longest row. Dorsum of head behind antennal insertions with more than 5 pairs of hairs. Dorsal alitrunk with 4 or more pairs of hairs. Head between frontal carinae with foveolate punctures, at least posteriorly. Scapes relatively somewhat longer, SI range 85-94.

A member of the Quadridens species group

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Afrotropical Region: Angola, Cameroun (type locality), Central African Republic, Equatorial Guinea, Gabon, Ghana, Ivory Coast, Nigeria, Uganda.


Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

The biology of most Pristomyrmex species is poorly known. From Wang (2003): Most species of Pristomyrmex dwell in the rainforest, foraging as predators or scavengers. An Asian species, Pristomyrmex punctatus, however, occurs in open and disturbed habitats (e.g., bare hills, agricultural areas, and beaches). These ants prefer to nest in soil, litter, or rotten wood; in rotten parts of living trees; in dead standing trees; or around plant roots.

Pristomyrmex is of great interest because it exhibits several unusual biological and evolutionary phenomena. The absence of morphologically normal queens and reproduction primarily by unmated workers in P. punctatus {=P. pungens) is a highly unusual life history in the Formicidae. Ergatoid queens, a special wingless female caste morphologically intermediate between the queen and the worker, are present in at least four species: Pristomyrmex punctatus, Pristomyrmex africanus, Pristomyrmex wheeleri, and Pristomyrmex mandibularis; two of them (P. africanus and P. wheeleri) possess both queen and ergatoid queen castes.

Simulating death, slowness of movement, and nocturnal foraging has been recorded in Pristomyrmex (Donisthorpe, 1946; Taylor, 1965; Weber, 1941). Colony size varies greatly among species, ranging from about a dozen to several thousand workers (Donisthorpe, 1946; Itow et al, 1984; Mann, 1919; Taylor, 1965, 1968).

Castes

Queen

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • orbiceps. Xiphomyrmex orbiceps Santschi, 1914d: 367, fig. 30 (w.) CAMEROUN. Wang, M. 2003: 458 (q.m.). Combination in Pristomyrmex: Santschi, 1916a: 51; in Hylidris: Weber, 1952: 18; in Pristomyrmex: Bolton, 1981b: 286. Senior synonym of laevigatus: Bolton, 1981b: 286.
  • laevigatus. Hylidris laevigatus Weber, 1952: 20, fig. 12 (w.) DEMOCRATIC REPUBLIC OF CONGO. Junior synonym of orbiceps: Bolton, 1981b: 286.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Description

Worker

Bolton (1981) - TL 2.9-3.4, HL 0.72-0.90, HW 0.75-0.94, CI 100-106, SL 0.62-0.74, SI 80-87, PW 0.48-0.62, AL 0.72-0.88 (25 measured).

Base of mandible usually with 1-2 rugulae present but these fading out distally so that the blade near the apical margin is almost or entirely smooth. Apical (masticatory) margin with strong apical and preapical tooth followed by a diastema and a broad basal tooth formed by the fusion of two basal denticles. In many specimens this broad basal tooth shows two points but with wear only a single blunt prominence remains. Clypeus frequently with a weak median longitudinal carina but this tends to be reduced, present only posteriorly, or entirely absent. Anterior clypeal margin equipped with small denticles, usually 5 in number, consisting of a median and 2 on each side. Degree of development of the denticles is variable, ranging from a bluntly crenulate appearance to very distinct. Frontal carinae present, running back at least to the level of the posterior margins of the eyes and strongly divergent in their anterior halves. Strongly developed scrobes absent but the sides between the frontal carinae and the eyes sloping outwards and flat to very shallowly concave. Maximum diameter of eye 0.14-0.19, about 0.18-0.21 x HW and usually with 7-9 ommatidia in the longest row, though in smaller individuals only 6 may be present. With the head in full-face view the occipital margin shallow concave to quite conspicuously indented medially, the sides convex. With the alitrunk in profile the pronotum armed with a low broad blunt tubercle, without the conspicuous acute teeth or spines seen in other species; in dorsal view these tubercles appearing as low bluntly rounded angles. Propodeum armed with a pair of spines which are usually longer than their basal width but which are variable in length and, at minimum, may be only as long as their basal width. Metapleural lobes prominent and rounded. Petiole and postpetiole in profile rounded, without acute angles. Dorsum of head between frontal carinae to occipital margin smooth and highly polished. Sides of head mostly smooth but with some scattered foveolate punctures in front of, below, and behind the eyes. These punctures are generally fairly conspicuous but in some individuals they may be faint or even vestigial, especially behind the eyes. In most specimens, but especially in larger ones, a few punctures occur on the side of the head on a line linking the posterior margins of the eyes with the posterior extension of the frontal carinae, but these are frequently vestigial or absent. Alitrunk, petiole, postpetiole and gaster unsculptured. Hairs very sparse, present on mouthparts, ventral surface of head and gastral apex, but otherwise as follows. Dorsum of head behind level of antennal insertions with 2-3 pairs of hairs along the line of the frontal carinae. Occipital corners with one pair of hairs, Dorsal alitrunk without hairs except for a single pair on the mesonotum, and this pair is frequently lost by abrasion. Petiole, postpetiole and first gastral tergite without hairs. Scapes and tibiae lacking hairs but with fairly conspicuous pubescence which is usually more obvious on the former than on the latter. Colour uniform blackish brown to black, the appendages lighter.

Queen

Wang (2003) - TL 3.24-3.59, HL 0.85-0.90, HW 0.91-0.99, CI 106-110, SL 0.74-0.79, SI 80-85, EL 0.23- 0.26, PW 0.70-0.77, AL 0.90-1.00, PPW 0.29-0.32, PPL 0.21-0.24, PPI 129-145 (n = 8).

General shape with normal caste differences from conspecific worker; eyes larger; mesonotum with more hairs than in the conspecific worker. Other characters similar to worker.

Male

Wang (2003) - Two male specimens, one collected in Ghana (Tafo, twig in leaf litter), by B. Bolton, and the second male in Ivory Coast (Orston Expt. Sta., 17 km. W. of Abidjan), by W. L. Brown, were originally mounted, respectively, together with one and two workers on the same pins: TL 2.58, 2.76; HL 0.48, 0.50; HW 0.47, 0.48; CI 96, 100, SL 0.18, 0.18; SI 38, 38; HWE 0.63, 0.66; EL 0.24, 0.26; PW 0.57, 0.58; AL 0.87, 0.92; PPW 0.20, 0.21; PPL 0.17, 0.18; PPI 117, 118 (n = 2).

Head, including the eyes, distinctly broader than long. Clypeus narrow, convex in middle; anterior clypeal margin transverse. Maximum diameter of the median ocellus 0.08 to 0.09. On the mesoscutum, notauli distinct, forming a Y shape; parapsidal furrows absent. Scuto-scutellar sulcus with 8 to 11 short ridges. Propodeum slightly tuberculate, lacking teeth or spines. Metapleural lobes subtriangular. Petiole node low in profile, with a fairly long anterior peduncle; its anterior face, together with the dorsal surface of the peduncle, forming a declivity. Postpetiole in profile low, rounded dorsally, and in dorsal view slightly broader than long. Dorsum of head gene rally smooth and shining, but with about 8 to 10 short rugae on the posterior clypeal margin. A few short rugae present on the frontal area. A weak, curved ruga present above the antennal insertion. Alitrunk gene rally smooth and shining, except for those marked sutures. Petiole, postpetiole, and gaster smooth and shining. All dorsal surfaces with abundant erect or suberect hairs. Scapes and tibiae with numerous suberect short hairs. Body reddish-brown; wings white or light-yellow.

Type Material

Bolton (1981):

Syntype workers, Cameroun: Victoria (Silvestri); and Ghana: Aburi (Silvestri) (Naturhistorisches Museum, Basel) [examined].

Hylidris laevigatus Holotype worker, Zaire: 13 miles [21 km] S. of Asa, lat. 4°40'N, long. 25°40'E., 3,iii.1948, no. 2170.1 (N. A. Weber) (American Museum of Natural History) [examined].

References

  • Bolton, B. 1981b. A revision of six minor genera of Myrmicinae (Hymenoptera: Formicidae) in the Ethiopian zoogeographical region. Bull. Br. Mus. (Nat. Hist.) Entomol. 43: 245-307 PDF (page 286, Combination in Pristomyrmex, Senior synonym of laevigatus)
  • Santschi, F. 1914d. Formicides de l'Afrique occidentale et australe du voyage de Mr. le Professeur F. Silvestri. Boll. Lab. Zool. Gen. Agrar. R. Sc. Super. Agric. 8: 309-385 (page 367, fig. 30 worker described)
  • Santschi, F. 1916a. Description d'un nouveau Formicide (Hym.) de l'Afrique occidentale. Bull. Soc. Entomol. Fr. 1916: 50-51 (page 51, Combination in Pristomyrmex)
  • Wang, M. 2003. A Monographic Revision of the Ant Genus Pristomyrmex (Hymenoptera:Formicidae). Bull. Mus. Comp. Zool. 157(6): 383-542 (page 456, figs. 264, 273 queen, male described)
  • Weber, N. A. 1952a. Studies on African Myrmicinae, I (Hymenoptera, Formicidae). Am. Mus. Novit. 1548: 1-32 (page 18, Combination in Hylidris)