Ocymyrmex okys

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Ocymyrmex okys
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Crematogastrini
Genus: Ocymyrmex
Species: O. okys
Binomial name
Ocymyrmex okys
Bolton & Marsh, 1989

Ocymyrmex okys casent0900407 p 1 high.jpg

Ocymyrmex okys casent0900407 d 1 high.jpg

Specimen Labels

Nothing is known about the biology of Ocymyrmex okys.

Identification

A member of the weitzeckeri group. The species closest related to okys is Ocymyrmex monardi, a taxon known from Namibia and Angola; both species belong in the weitzekeri-group. O. monardi is however a more slender species than okys, having the petiole and postpetiole longer than broad in dorsal view, and the petiole node lower and more shallowly convex in profile. Apart from this monardi is more uniformly coloured, not having the head and gaster strongly contrasting with the alitrunk as in okys. (Bolton and Marsh 1989)

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Afrotropical Region: Namibia (type locality).

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.

  • okys. Ocymyrmex okys Bolton & Marsh, 1989: 1299 (w.q.) NAMIBIA.

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

Description

Worker

Holotype. TL 7.5, HL 1.84, HW 1.72, CI 93, SL 1.52, SI 88, PW 1.10, AL 2.26.

Palp formula 3, 3, the left apical maxillary palpomere constricted near its midlength. Anterior clypeal margin with a conspicuous median notch or impression. With the head in full-face view the eyes distinctly failing to break the outline of the sides; the maximum diameter of the eye 0.22 x HW. Sides of head in front of eyes straight to extremely feebly concave; behind the eyes rounding into the occipital corners. Occipital margin with a shallow median indentation. Pronotum and anterior mesonotum evenly shallowly convex in profile, posterior portion of mesonotum sloping to the propodeum, the latter itself gently sloped posteriorly and rounding broadly and evenly into the steeply sloping declivity. Metapleural lobes rounded but prominent, in profile projecting beyond the bulge of the metapleural gland bulla and plainly visible. Petiole node relatively large and rounded in profile, in dorsal view slightly broader than long and distinctly broader than the posterior petiolar peduncle. Postpetiole broader than long, narrow anteriorly and rapidly broadening behind, the widest point just behind the midlength. First gastral segment constricted basally, the first tergite much longer than broad. Sculpture of cephalic dorsum coarse and dense. Behind the frontal lobes, and spanning the midline, is a longitudinal strip of irregular rugulae. The outer rugulae of the strip diverge posteriorly and arch outwards behind the eyes, becoming fainter laterally and tending to become confused with strong punctulate-granular ground-sculpture in this area. Between the eye and the antennal fossa on each side the sculpture is of fine dense irregular to chaotic rugulae, whose trend tends to be along an oblique line running towards the mandibular insertion. Sides of alitrunk densely and quite regularly costate to costate-rugose. Side of pronotum with more than 15 oblique longitudinal costae between the ventral margin and the level of the base of the mesothoracic spiracle. Petiole and postpetiole mostly very finely and faintly reticulate to reticulate-granular, in dorsal view the petiole anteriorly with faint and extremely fine transverse rugulae; the ventral surface with some stronger transverse rugulae. Pilosity moderately dense everywhere but sides of meso- and metapleuron without abundant outstanding pilosity. Head dull reddish, the petiole, postpetiole and gaster approximately the same colour or slightly lighter. Alitrunk blackish, in places with a very weak dull, reddish tint.

Paratypes. TL 6.3-7.3, HL 1.70-1.78, HW 1.60-1.65, CI 93-94, SL 1.48-1.56, SI 93-94, PW 1.04-1.07, AL 2.14-2.20 (2 measured). As holotype but somewhat smaller and the eyes marginally larger, maximum diameter 0.23 x HW.

Holotype Specimen Labels

Type Material

Holotype worker, Namibia: Windhoek, 1987, sample WHI (A.C. Marsh) (The Natural History Museum). Paratypes, 2 workers and 1 ergatoid female with same data as holotype (BMNH).

References