Ocymyrmex cavatodorsatus

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Ocymyrmex cavatodorsatus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Crematogastrini
Genus: Ocymyrmex
Species: O. cavatodorsatus
Binomial name
Ocymyrmex cavatodorsatus
Prins, 1965

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Specimen Labels

Nothing is known about the biology of Ocymyrmex cavatodorsatus.

Identification

The sole member of the cavatodorsatus group. As Prins points out, this species is related to Ocymyrmex barbiger in its lack of a basal gastral constriction. It is separated from barbiger by its lack of a clypeal impression, much reduced sculpture and strongly saddle-shaped alitrunk. In these aspects it seems closely related to Ocymyrmex turneri, another species without a gastral constriction, which also lacks a clypeal impression and has reduced sculpture. However, turneri has the alitrunk jet black, the clypeal margin prominent medially, the eyes large and breaking the outline of the sides of the head, the scapes with SI > 100 (apparently SI < 100 in cavatodorsatus) and has a transverse arched crest on the alitrunk at the promesonotal junction. (Bolton 1981)

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Afrotropical Region: Namibia, South Africa (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.

  • cavatodorsatus. Ocymyrmex cavatodorsatus Prins, 1965c: 1021, figs. 1, 2 (w.) SOUTH AFRICA. Bolton & Marsh, 1989: 1278 (q.). See also: Bolton, 1981b: 266.

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 4.5, HL 1.02, AL 1.41. Anterior clypeal margin without a semicircular median impression. Eyes not breaking outline of sides of head in full-face view. Alitrunk in profile characteristically shaped, with the promesonotum forming a single high, strongly arched convexity, the posterior mesonotum and anterior propodeum forming a uniform deep concavity and the remainder of the propodeum arching upwards again posteriorly before rounding narrowly into the deep and almost vertical declivity; the entire alitrunk having a strong saddle-shaped appearance in profile. Petiole node high-subconical in profile, longer than broad in dorsal view. Postpetiole broader than long in dorsal view. Base of first gastral tergite in dorsal view without a neck-like constriction, the sides of the tergite evenly convex behind the point of articulation with the postpetiole. Dorsum of head from level of eyes to occiput smooth and shining. Promesonotal arch dorsally smooth and shining, including the area between the meso thoracic spiracles. Remainder of dorsal alitrunk with faint transverse rugae which are almost effaced; the propodeal declivity smooth. Head bright red to yellowish red, the alitrunk yellowish red to brick red, the gaster distinctly darker, piceous.

Type Material

Syntype workers, South Africa: Cape Prov., Dist. Upington, Louisvale, 6.viii.l964, AcAx 3412 (A. J. Prins) (Res. Inst. for Plant Protection, Pretoria, South Africa).

References