Ocymyrmex kahas

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

Ocymyrmex kahas casent0900400 p 1 high.jpg

Ocymyrmex kahas casent0900400 d 1 high.jpg

Specimen Labels

Nothing is known about the biology of Ocymyrmex kahas.

Identification

This distinctive species is characterized by its strong clypeal flange, eyes which break the outline of the sides of the head, PF 4,3, and unconstricted gastral base with both tergite and sternite convex basally in profile. At first glance it is reminiscent of Ocymyrmex barbiger, Ocymyrmex cilliei, Ocymyrmex robustior and Ocymyrmex dekerus, but all of these lack the very broad clypeal flange and have a strong median longitudinal impression or groove along the postpetiolar sternite. The closest relatives of kahas are Ocymyrmex afradu and Ocymyrmex flavescens, which share the characteristic clypeal and postpetiolar structure of kahas, and which together constitute the kahas-group. kahas and flavescens have the gaster yellowish, afradu has the gaster black; kahas and flavescens have the petiolar peduncle longer than the node whilst afradu has the node slightly longer than the peduncle. In full-face view the occipital margin is more strongly indented medially in afradu and flavescens than in kahas, and in afradu the petiole node is long, low and subclavate in profile. (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

Known only from the worker caste.

Nomenclature

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

  • kahas. Ocymyrmex kahas Bolton & Marsh, 1989: 1298, figs. 11, 16 (w.) 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 6.7, HL 1.72, HW 1.54, CI 90, SL 1.56, SI 101, PW 0.95, AL 2.00.

Anterior clypeal margin with a small notch medially. Margin of clypeus with a broad projecting cuticular flange. Palp formula 4,3. With the head in full-face view the outer curve of the eyes just breaking the outline of the sides of the head. Maximum diameter of eye 0.36, about 0.23 x HW. Sides of head in front of eyes more or less straight and very feebly divergent anteriorly. Behind the eyes the sides converging posteriorly and rounding into the relatively broad occipital margin; the latter very feebly indented medially. With alitrunk in profile the pronotum rising steeply from the cervical shield and only very shallowly convex dorsally. Propodeal dorsum feebly convex and rounding posteriorly into the weakly convex declivity. Bulla of metapleural gland not strongly projecting posteriorly, the narrow metapleural lobe and the carina linking the lobes across the declivity, clearly visible in profile. Petiole node in dorsal view about as broad as long, postpetiole slightly broader than long. Sternite of postpetiole ventrally shallowly and inconspicuously concave medially, lacking a deep median longitudinal impression or groove. In profile the outlines of the first gastral tergite and sternite are each shallowly convex from their articulation with the postpetiole. In dorsal view the base of the gaster is not constricted. Dorsum of head finely and densely longitudinally rugulose, the rugulae faint and feebly wavy to very weakly sinuate. Ground-sculpture between the rugulae faint and feeble, but the surface not glassy smooth. Dorsal alitrunk mostly densely and finely transversely rugose but with a patch of longitudinal sculpture between the mesothoracic spiracles. Sides of alitrunk with regularly spaced strong dense rugae, the spaces between which are wider than the rugae themselves. On the sides of the pronotum about 16 rugae are present between the base of the mesothoracic spiracle and the ventral margin of the sclerite. Ground-sculpture on sides of alitrunk superficial and minimal, so that the rugae stand out in sharp relief. Petiole and postpetiole mostly feebly reticulate, the petiole node with some extremely faint vestiges of transverse sculpture dorsally and with some stronger transverse rugulae ventrally. All dorsal surfaces of head and body with spaced out standing hairs present. Head a dull orange-red, the gaster more yellowish so that the gaster is somewhat lighter in shade than the head. Alitrunk darker, dull reddish to reddish brown.

Paratypes. TL 6.3-7.0, HL 1.64-1.74, HW 1.44-1.56, CI 87-91, SL 1.48-1.56, SI 100-104, PW 0.88-0.96, AL 1.88-2.00 (8 measured). Maximum diameter of eye 0.33-0.36, about 0.23-0.25 x HW. Sides of pro no tum with 13-16 rugae between base of mesothoracic spiracle and ventral margin. In some para types the cephalic rugular sculpture diverges more strongly posteriorly than in the holotype, and in these a small area of U-shaped rugular sculpture may occur centrally close to the occipital margin.

Type Material

Holotype worker, Namibia ( = South West Africa): Khorixas, 20 deg. 19 min. S., 14 deg. 57 min. E., 20.iii.1982, sample KHI (A.C. Marsh) (The Natural History Museum). Paratypes, 8 workers with same data as holotype (BMNH, SAM, Museum of Comparative Zoology).

References