Ocymyrmex hirsutus

AntWiki - Where Ant Biologists Share Their Knowledge
Jump to: navigation, search
Ocymyrmex hirsutus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Crematogastrini
Genus: Ocymyrmex
Species: O. hirsutus
Binomial name
Ocymyrmex hirsutus
Forel, 1910

Ocymyrmex hirsutus casent0900409 p 1 high.jpg

Ocymyrmex hirsutus casent0900409 d 1 high.jpg

Specimen Labels

Nothing is known about the biology of Ocymyrmex hirsutus.

Identification

A member of the hirsutus group. Apart from its dense pilosity hirsutus can quickly be recognized by the distinctive sculpture of the head, as described in the description. Transverse sculpture on the area of the head behind the eyes is also found in Ocymyrmex robecchii and in females of the various species of Ocymyrmex, but in all of these the sculpture consists of regular transverse costulae, not narrowly vermiculate rugulae. (Bolton 1981)

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Afrotropical Region: Botswana (type locality), South Africa.

Distribution based on AntMaps

AntMapLegend.png

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.

  • hirsutus. Ocymyrmex weitzeckeri subsp. hirsutus Forel, 1910f: 13 (w.) BOTSWANA. Bolton & Marsh, 1989: 1278 (q.). Raised to species: Santschi, 1914a: 431. See also: Bolton, 1981b: 271.

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 6.9-7.8, HL 1.54-1.82, HW 1.48-1.74, CI 93-97, SL 1.40-1.62, SI 90-95, PW 0.96-1.14, AL 2.04-2.36 (7 measured).

Anterior clypeal margin with a conspicuous semicircular median impression which is flanked by a pair of teeth or denticles. Occipital margin in full-face view slightly indented or flattened to feebly concave medially, not evenly transversely convex. Maximum diameter of eye 0.32-0.38, about 0.21-0.23 x HW. Alitrunk in profile with promesonotum evenly convex, sloping behind to the propodeum. Dorsum of propodeum sloping very weakly, rounding broadly and evenly into the declivity. Metapleural lobes short and bluntly triangular. Petiole in profile with a small, low, evenly rounded node, the peduncle without a ventral process but broadly and very shallowly sinuate in some workers. Petiole node in dorsal view varying from as broad as long to distinctly broader than long. Postpetiole dorsally longer than broad. Base of first gastral tergite constricted and forming a narrow neck behind the postpetiole. Rugulose sculpture on dorsum of head fine, irregular and very densely packed, with fine punctulate to granular ground-sculpture between the narrow rugulae. To the level of the posterior margins of the eyes the rugulae are mostly or entirely longitudinal to arched-longitudinal, the pattern varying from specimen to specimen. Behind this level the rugulae are transverse or arched-transverse, tightly packed and narrowly vermiculate. In some the rugulae are so fine and close together, and so narrowly vermiculate, that the occipital sculpture appears as a disorganised mass of narrow irregular wiggly transverse lines. Dorsal alitrunk and declivity of propodeum transversely rugose except between the mesothoracic spiracles where the sculpture is longitudinal. Extent of this longitudinally sculptured area variable, the further forward the rugae extend the more strongly arched is the transverse sculpture of the pronotum. In some the pronotal dorsum is mostly arched-longitudinally rugose. Sides of alitrunk rugose, the sides of the pronotum finer and less densely so than the pleurae. Petiole with a few transverse rugae ventrally and the peduncle also with a few dorsally, but otherwise the segment only superficially sculptured. Postpetiole unsculptured. All dorsal surfaces of head and body except first gastral tergite densely clothed in acute hairs of varying length, very numerous on the dorsal alitrunk. On the sides of the pronotum the hairs are directed forwards; on the pleurae they point backwards and downwards. First gastral tergite with sparse short hairs on the surface and with a denser transverse apical row. Colour reddish, the gaster the same colour as the alitrunk or lighter.

Syntype Specimen Labels

Type Material

Bolton (1981) - Syntype workers, Botswana: Severelela and Kooa (L. Schultze) (Musee d'Histoire Naturelle Genève) [examined].

References