Ocymyrmex afradu

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

Ocymyrmex afradu casent0900399 p 1 high.jpg

Ocymyrmex afradu casent0900399 d 1 high.jpg

Specimen Labels

Nothing is known about the biology of Ocymyrmex afradu.

Identification

Bolton and Marsh (1989) - afradu is closest related to Ocymyrmex kahas and Ocymyrmex flavescens, two other Namibian species. Apart from this, 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.

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

Only known from the worker caste.

Nomenclature

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

  • afradu. Ocymyrmex afradu Bolton & Marsh, 1989: 1288 (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 5.8, HL 1.44, HW 1.36, CI 94, SL 1.34, SI 99, PW 0.84, AL 1.70.

Anterior clypeal margin with a broad and conspicuous cuticular flange, similar to that seen in kahas. Clypeus with a small and shallow anteromedian impression. Palp formula variable, not clearly visible in holotype but the single para type has the left maxillary palp with 4 segments, the right with 3; labial palpi both 3-segmented. Maximum diameter of eye 0.34, about 0.24 x HW. In full-face view the eyes distinctly breaking the outline of the sides of the head. Sides of head in front of eyes almost parallel, scarcely diverging anteriorly. Behind the eyes the sides convex and converging posteriorly, rounding broadly into the occipital margin which is itself indented medially. Promesonotum evenly convex in profile, the outline of the posterior portion of the mesonotum sloping and very shallowly concave. Propodeal dorsum weakly convex and rounding broadly and very evenly into the shallowly convex declivity. Bulla of metapleural gland projecting posteriorly and in profile almost obscuring the narrow and evenly rounded metapleural lobes. Petiole in profile with a relatively short peduncle and an elongate low subclaviform node; the length of the node slightly greater than that of the peduncle. In dorsal view the petiole node longer than broad, the postpetiole broader than long and broadest posteriorly. Sternite of postpetiole ventrally almost transverse, with only the shallowest concavity; lacking a strongly defined median longitudinal groove or impression. Gaster in profile with both the first tergite and the first sternite having shallowly convex outlines from their articulation with the postpetiole, lacking a basal constriction. In dorsal view the gaster without a narrow neck-like basal constriction. Dorsum of head glossy, very finely and weakly longitudinally costulate, and with ground-sculpture between the costulae very faint to absent. Cephalic costulae become weaker posteriorly and are almost effaced close to the occipital margin. Dorsal alitrunk evenly transversely sculptured except on pronotum where a patch of longitudinal sculpture runs forward from between the mesothoracic spiracles; the remaining dorsal pronotal sculpture arches around this patch and is relatively faint. Sides of alitrunk regularly sharply costulate everywhere, the individual costulae narrower and more widely spaced on sides of pronotum than elsewhere. Ground-sculpture faint to absent. Petiole with a few weak transverse rugae beneath the node but dorsally with extremely fine and very crowded faint ripple-like transverse rugulae; these are fainter still and tend to peter out on the sides of the node. Postpetiole feebly reticulate. First gastral tergite with superficial reticular patterning basally, which fades out apically on the sclerite. All dorsal surfaces of body with fine white to silvery hairs present. Head glossy dull red, remainder of body black but in places with a reddish or brownish tint.

Type Material

Holotype worker, Namibia ( = South West Africa): Namib Desert, Hunkab River, Skeleton Coast, 19 deg. 43 min. S., 13 deg. 11 min. E., 16.viii.1982, sample SC5 (A. C. Marsh) (The Natural History Museum). Paratype. One worker (dissected) with same data as holotype (BMNH). Dissected and mounted ventral side uppermost to show mouth-parts and ventral surfaces of body.

References