| Ocymyrmex barbiger|
Nothing is known about the biology of Ocymyrmex barbiger.
A member of the barbiger group. One of three known species in which the base of the first gastral tergite is not constricted to a narrow neck, barbiger is separable from both others showing this character (Ocymyrmex cavatodorsatus, Ocymyrmex turneri) by its possession of an impressed anterior clypeal margin and its strong sculpture. (Bolton 1981)
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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.
The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.
- barbiger. Ocymyrmex barbiger Emery, 1886: 364, pl. 17, figs. 9-11 (w.m.) SOUTH AFRICA. [Misspelled as barbatus by Emery, 1892a: 114.] Bolton, 1981b: 261 (q.). See also: Bolton & Marsh, 1989: 1291.
Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.
Bolton (1981) - TL 6.7-7.2, HL 1.54-1.84, HW 1.42-1.76, CI 90-97, SL 1.38-1.58, SI 87-98, PW 0.94-1.10, AL 2.00-2.20 (20 measured).
Anterior clypeal margin with a semicircular median impression which is flanked by a pair of teeth. The impression is usually deep and conspicuous but in some individuals may be broad and quite shallow. The flanking teeth are generally well developed but commonly are broadly triangular and blunted, sometimes little more than broadly rounded prominences. Maximum diameter of eye 0.32-0.35, about 0.19-0.22 x HW, in full face view not breaking the outline of the sides of the head. Promesonotum forming an evenly rounded low convexity which slopes downwards behind to the propodeum, the dorsum of which varies from more or less flat to slightly inclined. Propodeal dorsum rounding broadly and evenly into the declivity. Metapleural lobes low but prominent, their free edges rounded to bluntly truncated posteriorly. Petiole node in profile usually quite high, bluntly rounded-subconical in shape, but sometimes the dorsum more flattened and the node appearing less regular in shape. Petiole node in dorsal view usually broader than long, less commonly only about as broad as long. Postpetiole always broader than long in dorsal view, discounting the anterior articulating portion. Base of first gastral tergite without a neck-like constriction. Head finely and densely rugulose, with fine punctulate ground-sculpture; the pattern formed by the rugulae very variable on the dorsum but apparently following a step by step change. In many the cephalic rugulae are regular and longitudinal, parallel on the central strip and running straight back to the occipital margin, but the more lateral rugulae tending to diverge and arch outwards behind the eyes. This seems the basic pattern from which the following derive sequentially. Firstly, the median-line rugulae begin to diverge posteriorly, forcing the more lateral rugulae to arch outwards even more. Next, the point at which the median-line rugulae begin to diverge shifts gradually forward, arching the lateral components more strongly outwards all the time. When the point of divergence of the mid-line rugulae has shifted a certain distance forwards a number of V-shaped rugulae appear in front of the impression in the centre of the occipital margin, which occupy the space vacated by the now divergent mid-line rugulae. Then, as the point of divergence of the mid-line rugulae shifts still further forward the V -shaped rugulae also shift forward on the head and their angle becomes more obtuse the further forward they shift. This process continues until ultimately the head is mostly transversely sculptured behind the eyes, although the rugulae tend to retain their broadly V -shaped nature more posteriorly on the head. Pronotal dorsum usually with extensive longitudinal sculpture, the more lateral components arching across in front of the central longitudinals. Space between mesothoracic spiracles usually longitudinally rugose, sometimes obliquely so and very rarely the sculpture here more or less transverse. Remainder of dorsal alitrunk transversely rugose. Petiole with transverse rugulae ventrally which usually extend for some distance up the sides of the node, commonly to the dorsum. In more strongly sculptured samples the rugulae continue across the top of the node but often the dorsum is more weakly sculptured. Postpetiole finely shagreened or with fine superficial patterning only. All dorsal surfaces of head and body with hairs, those on the first gastral tergite more numerous and longer in barbiger than is usual in the genus, the gastral hairs frequently approaching the length and density seen on the alitrunk. Elsewhere in the genus gastral hairs on the first tergite are much shorter and much sparser than on the alitrunk. Colour of head and alitrunk orange to dull brick red, the gaster darker, frequently dull brown with a reddish tint or even blackish brown.
- Bolton, B. 1981. A revision of six minor genera of Myrmicinae (Hymenoptera: Formicidae) in the Ethiopian zoogeographical region. Bulletin of the British Museum (Natural History) Entomology. 43:245-307. PDF (page 261, queen described)
- Bolton, B. and A. C. Marsh. 1989. The Afrotropical thermophilic ant genus Ocymyrmex (Hymenoptera: Formicidae). Journal of Natural History. 23:1267-1308.PDF (page 1291, see also)
- Emery, C. 1886b. Alcune formiche africane. Bull. Soc. Entomol. Ital. 18: 355-366 (page 364, pl. 17, fig. 9-11 worker, male described)