Ocymyrmex turneri

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Ocymyrmex turneri
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Crematogastrini
Genus: Ocymyrmex
Species: O. turneri
Binomial name
Ocymyrmex turneri
Donisthorpe, 1931

Ocymyrmex turneri casent0900393 p 1 high.jpg

Ocymyrmex turneri casent0900393 d 1 high.jpg

Specimen Labels

Marsh (1986b) says that turneri is a diurnally foraging scavenger, primarily seeking out dead insects. Its nests are inconspicuous and have a single entrance hole. O. turneri is widespread on the Namib gravel plains and occurs across the entire width of the desert (Marsh, 1986a).

Identification

A member of the velox group. O. turneri is one of the smallest species known in the genus and is easily distinguished from all others by having an unconstricted base to the gaster, large eyes which break the outline of the sides of the head, reduced sculpture, relatively long antennal scapes and a clypeal margin which projects medially into a low triangular prominence. (Bolton 1981)

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Afrotropical Region: Namibia (type locality), South Africa.

Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Little is known about the biology of this species but a few species of Ocymyrmex have been studied in some detail. From this we can form some ideas about the biology of the genus as a whole. The following is summarized from Bolton and Marsh (1989). More details can also be found on the Ocymyrmex genus page.

Arnold (1916) observed that Ocymyrmex species with which he was acquainted nested in the ground in hot arid areas. The nests themselves went very deep into the ground, usually in loose sandy soil, and had a crater-like entrance. The ants used their well-developed psammophores to carry soil particles excavated from the nests. Recently both Marsh and Robertson (pers. comm.) have observed that workers of Ocymyrmex fortior close the nest entrance with small stones during periods of nest inactivity. Also, in Zimbabwe, fortior workers have been seen adding small stones to the crater-like nest entrance that were picked up from the ground some distance away from the nest. Species are now known which nest in very rocky soil and the nests may extend through the bedrock itself, necessitating the use of a large crowbar to expose the nest-chambers (H. Robertson, pers. comm.). Careful excavations of nests in well-structured sandy soil by one of us (Marsh) have revealed a simple nest structure. For example, nests of foreli typically have one entrance that opens into a vertical tunnel which terminates in a broad chamber at a depth of about 30 cm. Other brood and food chambers branch off from the tunnel at various intermediate levels. In most nest excavations the ergatoid queen was discovered near the bottom of the nest. In very unstructured loose sand, such as in the dry river beds of the Namib Desert, the tunnels and chambers of Ocymyrmex nests followed the root systems of shrubs and trees, and the major tunnel was therefore not necessarily vertical. Colonies of Ocymyrmex range in size from 200 to 1000 individuals (Marsh, 1987).

Other general aspects of their biology include workers that move rapidly, erratically, and are often active during the hottest part of the day. Specifics of their diet seem to vary by species but can include seeds and insects. For most species where queens are known they are worker-like ergatiod forms that are nonetheless clearly a morphologically distinct caste, as opposed to many intercaste ergatiods known from other genera that are intermediate between workers and more robust queens. Males of Ocymyrmex are often collected at lights but males associated with conspecific workers and females have rarely been collected.

Castes

Nomenclature

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

  • turneri. Ocymyrmex turneri Donisthorpe, 1931b: 499 (w.) NAMIBIA. Bolton & Marsh, 1989: 1278 (q.). See also: Bolton, 1981b: 279; Bolton & Marsh, 1989: 1305.

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

Description

Worker

Bolton and Marsh (1989) - TL 5.5-5.8, HL 1.38-1•40, HW 1.24-1.28, CI 89-91, SL 1.37-1.40, SI 109-111, PW 0.75-0.80, AL 1.70-1.80. Maximum diameter of eye is 0.26-0.28 x HW (10 measured).

In the new series the sides of the pronotum are somewhat more extensively sculptured than in the holotype, and their dense dorsal pilosity indicates that earlier conjecture regarding abrasion of the holotype was correct. Similarly, the dorsal alitrunk of the new series is feebly sculptured, this area being mostly smooth in the holotype. Hamish Robertson (University of the Witwatersrand) collected a single specimen at the same locality. This matches the preceding but has the median clypeal prominence somewhat flattened and inconspicuous, truncated rather than bluntly triangular at its apex.

Bolton (1981) - TL 5.8, HL 1.40, HW 1.28, CI 91, SL 1.40, SI 109, PW 0.80, AL 1.76. Small species. Anterior clypeal margin without a median impression, on the contrary the middle of the anterior clypeal margin projecting forward as a low, broad triangular prominence. Eyes relatively large, maximum diameter 0.36, about 0.28 x HW. In full-face view the eyes very conspicuously breaking the outline of the sides of the head. Antennal scapes relatively long, SI > 100. Promesonotum in profile rounded, with a low transversely arched crest running across the dorsum at the junction of pronotum and mesonotum, arching forward from the mesothoracic spiracle on each side. Posterior part of mesonotum and anterior part of propodeum concave in profile, the posterior portion of the propodeum convex and curving evenly into the declivity behind. Petiole node in profile high, subconical, with a narrowly rounded dorsum, the posterior face convex, the anterior face longer, almost flat and less steeply sloped than the posterior face. Petiole node in dorsal view longer than broad, the postpetiole broader than long. First gastral tergite without a constricted basal neck. Dorsum of head glossy, sculptured with very feeble superficial rugulae which are transversely arched and are almost effaced occipitally. Ground-sculpture between the faint rugulae absent. Dorsal alitrunk unsculptured, smooth and highly polished except for vestiges of faint transverse rugulae on the extreme anterior portion of the pronotum and the propodeal declivity. On the sides of the alitrunk the pleurae with strong, widely spaced and roughly parallel rugae, otherwise unsculptured except for vestiges on the sides of the pronotum near the base. Petiole and postpetiole only with faint superficial patterning which is almost effaced in places. All dorsal surfaces of head and body with scattered hairs of varying length but the holotype (and only known specimen) appears to be considerably abraded and in life this species may well be as hairy as other species in the genus. Alitrunk jet black and shiny, head and gaster blackish brown.

Type Material

Bolton (1981) - Holotype worker, South West Africa: Walvis Bay, l.xii.1927 (R. E. Turner) (The Natural History Museum) [examined].

References