Ocymyrmex engytachys

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

Ocymyrmex engytachys casent0900401 p 1 high.jpg

Ocymyrmex engytachys casent0900401 d 1 high.jpg

Specimen Labels

Nothing is known about the biology of Ocymyrmex engytachys.

Identification

A member of the tachys group. O. engytachys forms a close species-pair with Ocymyrmex tachys.

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.

  • engytachys. Ocymyrmex engytachys Bolton & Marsh, 1989: 1294 (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 5.5, HL 1.34, HW 1.19, CI 89, SL 1.26, SI 106, PW 0.76, AL 1.62.

Very closely related to tachys and sharing all the main characters of that species, including the extremely reduced PF 2, 3 and those characters mentioned in the notes on the species-groups. Otherwise answering to the description of tachys given below except for the following.

Anterior clypeal margin of engytachys with a shallow and inconspicuous median impression.

Sculpture of sides of alitrunk the same density as in tachys but more strongly developed, the sides of the ant appearing coarsely rugose. Dorsum of petiole node with rugulae stronger and more extensive than in tachys.

Maximum diameter of eye 0.29, about 0.24 x HW.

Colour very different from tachys. The head unicolourous dull orange-red, without lighter mandibles or anteriormost portion of head. Alitrunk red. Gaster blackish brown, much darker than both head and alitrunk.

Paratype. TL 5.4, HL 1.30, HW 1.16, CI 89, SL 1.23, SI 106, PW 0.74, AL 1.54.

Maximum diameter of eye 0.25 x HW. Very similar to holotype but cephalic sculpture different. In the holotype the cephalic dorsum is finely irregularly longitudinally rugulose, with distinctive punctu1ate ground-sculpture. In the paratype the rugular component is almost completely suppressed and the punctulate ground-sculpture more intense and obvious.

Type Material

Holotype worker, Namibia: Namib Desert, 35 km E. of Gamsberg Pass, x.1987, ND3B (A. C. Marsh) (The Natural History Museum). Paratype, one worker with same data as holotype (BMNH).

References