Ocymyrmex micans

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Ocymyrmex micans
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Crematogastrini
Genus: Ocymyrmex
Species: O. micans
Binomial name
Ocymyrmex micans
Forel, 1910

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Specimen Labels

A Namibia saltpan baiting study found Ocymyrmex micans, Pheidole tenuinodis and a Tetramorium sp. were the behaviorally and numerical dominant ant species in this habitat.

Identification

A member of the hirsutus group. O. micans, known from Namibia and South Africa, is most closely related to the widely distributed Ocymyrmex fortior. The two are separated on cephalic sculpture which is stronger, more sharply defined and more regular in fortior, and the punctulate ground-sculpture never dominates the rugulose/costulate component in this species. Besides this, the postpetiole of fortior is relatively long and narrow, always longer than broad, whereas in micans the postpetiole is distinctly swollen posteriorly and its width exceeds its length. Similarly, the petiole node in dorsal view is always markedly expanded in micans, only moderately so in fortior. (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

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.

  • micans. Ocymyrmex weitzeckeri var. micans Forel, 1910f: 12 (w.) NAMIBIA. Raised to species: Bolton, 1981b: 272.

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 6.2-6.9, HL 1.54-1.70, HW 1.40-1.56, CI 91-92, SL 1.38-1.44, SI 92-98, PW 0.92-1.00, AL 2.00-2.16 (2 measured).

Anterior clypeal margin with a semicircular median impression which is flanked by a pair of small teeth. Occipital margin very slightly concave or indented medially. Maximum diameter of eye 0.32-0.36, about 0.23 x HW. With alitrunk in profile the promesonotum evenly shallowly convex. Propodeal dorsum rounding broadly and evenly into the declivity. Metapleural lobes small and only feebly projecting, in profile mostly or wholly concealed by the bulge of the metapleural glands. Petiole node well defined, the dorsum narrowly and evenly rounded in profile, dome-like. Postpetiole swollen, the tergite low in front then rising behind into a distinctly convex, smoothly rounded node. In dorsal view the petiole node broad and conspicuous, its maximum width slightly greater than the distance from the spiracle to the apex of the petiolar collar where it articulates with the postpetiole. Postpetiole in dorsal view narrow in front, becoming much broader behind, the width greater than the length. Base of first gastral tergite strongly constricted and forming a narrow neck behind the postpetiole. Sculpture of dorsum of head of dense, closely packed fine longitudinal irregular rugulae which, away from the midline in the area behind the level of the eyes, curve out towards the occipital corners. Behind the level of the eyes a conspicuous punctulate ground-sculpture is present which in places may be the dominant component of the sculpture. Where this is the case the rugulae are distinctly uneven, becoming wavy or even vermiculate. Dorsal alitrunk and propodeal declivity transversely rugose except between the mesothoracic spiracles where the sculpture is longitudinal. On the pronotum the rugae are arched-transverse around the longitudinal component. Sides of alitrunk regularly rugose, the rugae weakest and most widely spaced on the sides of the pronotum. Petiole and postpetiole unsculptured or the former with a few weak transverse rugulae ventrally and scattered vestigial marks elsewhere. All dorsal surfaces of head and body with numerous hairs of varying length except for the first gastral tergite where the hairs are short and sparse. Colour orange to orange-red, the gaster lighter in shade than the alitrunk.

Type Material

Bolton (1981) - Holotype worker, South West Africa: Okahandja (Peters) (Musee d'Histoire Naturelle Genève) [examined].

References