Ocymyrmex nitidulus

AntWiki - Where Ant Biologists Share Their Knowledge
Jump to: navigation, search
Ocymyrmex nitidulus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Crematogastrini
Genus: Ocymyrmex
Species: O. nitidulus
Binomial name
Ocymyrmex nitidulus
Emery, 1892

Ocymyrmex nitidulus casent0280940 p 1 high.jpg

Ocymyrmex nitidulus casent0280940 d 1 high.jpg

Specimen Labels

Bolton (Bolton and Marsh 1989) has observed from dissections that the ergatiod like queens of this species have larger, and many more, ovaries than workers.

Identification

A member of the weitzeckeri group. Only nitidulus and Ocymyrmex celer, among the species with the clypeus impressed and gaster constricted basally, lack strong ground-sculpture between the costulae or rugulae of the dorsal head. This gives them a slick and very polished appearance which immediately separates them from their allies in which granular or punctulate ground-sculpture is present, and which in consequence are dull and less polished. O. nitidulus and celer are separated by the shape of the pronotum, which is flat in the latter, rounded in the former, and by the shape of the head which is longer and narrower in celer than in nitidulus.(Bolton 1981)

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Afrotropical Region: Ethiopia, Kenya, Somalia (type locality), Uganda, United Republic of Tanzania.

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

Worker

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • nitidulus. Ocymyrmex robecchii r. nitidulus Emery, 1892a: 116 (q., not w.) SOMALIA. Emery, 1896i: 157 (m.); Bolton, 1981b: 274 (w.). Raised to species: Bolton, 1981b: 274.

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 7.4-7.8, HL 1.70-1.90, HW 1.64-1.82, CI 96-100, SL 1.48-1.60, SI 86-96, PW 1.08-1.20, AL 2.20-2.30 (20 measured).

Anterior clypeal margin with a conspicuous median semicircular impression which is flanked on each side by a low tooth or denticle, this tooth usually quite low and rounded, uncommonly strongly prominent. Maximum diameter of eye 0.34-0.40, about 0.20-0.22 x HW. The promesonotum evenly and broadly convex, sloping posteriorly to the propodeal dorsum; the latter rounding evenly into the declivity. Metapleural lobes small and low, bluntly rounded or broadly and bluntly truncated, sometimes reduced to a narrow little-projecting strip. Petiole node in profile small, low and smoothly rounded. In dorsal view the petiole node varying from slightly longer than broad to slightly broader than long. Postpetiole as broad as long to slightly broader than long in dorsal view. First gastral tergite constricted and forming a neck basally. Dorsum of head sculptured with low, rounded, feeble longitudinal costulae which may be very reduced or even effaced in places. Spaces between the costulae without ground sculpture, the surface smooth and polished, with a slick and glossy appearance. Sides of alitrunk closely and finely sharply constulate, the dorsum sharply transversely costulate except between the mesothoracic spiracles where the sculpture is usually longitudinal. Pronotal dorsum in front of the longitudinal sculpture finely arched-costulate to smooth, the sculpture always weaker than elsewhere on the alitrunk, sometime partially or wholly effaced or the costulae reduced to vestiges. This weakening of the sculptural intensity may also affect the longitudinal costulae between the mesothoracic spiracles. Ventral surface of petiole node with a few transverse rugulae which may be very feeble but which normally extend for some distance up the sides of the node before fading out. Dorsum of petiole node unsculptured or at most with vestiges remaining. Dorsum of peduncle usually with transverse fine rugulae but these may be very reduced and faint. Post petiole unsculptured or at most with some fine superficial patterning. All dorsal surfaces of head and alitrunk with numerous hairs of varying length, the first gastral tergite with hairs shorter and sparser than elsewhere. Colour glossy dull red, the gaster darker, blackish brown to black; entire body with a polished and shining appearance.

Type Material

Bolton (1981) - Holotype female [not worker], Somali Republic: Obbia (Robecchi) (Museo Civico di Storia Naturale, Genoa) [examined].

References