Ocymyrmex robecchii

Ocymyrmex robecchii
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Myrmicinae
Tribe:	Crematogastrini
Genus:	Ocymyrmex
Species:	O. robecchii
Binomial name
Ocymyrmex robecchii Emery, 1892 Specimen Labels

Nothing is known about the biology of Ocymyrmex robecchii.

Identification

A member of the weitzeckeri group. A large and conspicuous species, robecchii is characterized by its strongly impressed median clypeal notch, transverse cephalic sculpture, strongly impressed occipital margin, long scapes and large size. Although the two specimens seen possess the transverse cephalic sculpture characteristic of females in this genus, they lack the associated characters of shorter thicker scapes and broader, more parallel-sided frontal lobes which are usually associated with this caste (see discussion under the generic diagnosis). For this reason I have chosen to treat these specimens as bona fide workers for the time being, and have used the direction of cephalic sculpture as a key character In case they do not turn out to be females. This of course cannot be ascertained until more material becomes available. (Bolton 1981)

Keys including this Species

• Key to Ocymyrmex

Distribution

Distribution based on Regional Taxon Lists

Afrotropical Region: Kenya, Somalia (type locality).

Distribution based on AntMaps

Distribution based on AntWeb specimens

Check data from AntWeb

Countries Occupied

Number of countries occupied by this species based on AntWiki Regional Taxon Lists. In general, fewer countries occupied indicates a narrower range, while more countries indicates a more widespread species.

Estimated Abundance

Relative abundance based on number of AntMaps records per species (this species within the purple bar). Fewer records (to the left) indicates a less abundant/encountered species while more records (to the right) indicates more abundant/encountered species.

Biology

Explore Overview of Ocymyrmex 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. ‎

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

• robecchii. Ocymyrmex robecchii Emery, 1892a: 114, fig. (w.) SOMALIA. Menozzi, 1922a: 353 (m.). See also: Bolton, 1981b: 276.

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 9.2-9.3, HL 2.20-2.22, HW 2.02-2.04, CI 92, SL 2.08-2.16, SI 103-106, PW 1.26-1.28, AL 2.52-2.60 (2 measured).

Anterior clypeal margin with a strong semicircular median impression flanked by a pair of short rounded denticles. The head longer than broad (CI < 100), with sides which converge posteriorly, and with the occipital margin strongly impressed medially. Maximum diameter of eye 0.40, about 0.20 x HW. Scapes long, SI > 100. With alitrunk in profile the mesonotum anteriorly forming a distinct hump behind the pronotum, the two not forming a single continuous convexity. Orifices of mesothoracic spiracles protected by a pair of low tumuli or welts which project from the surface. Mesonotal dorsum sloping shallowly downwards posteriorly and confluent with the propodeal dorsum which is flat to very feebly concave to the level of the spiracle where it becomes shallowly convex and rounds broadly and evenly into the declivity. Metapleural lobes large and strongly developed, prominent, broadly subtriangular in shape and slightly upcurved. Peduncle of petiole without a ventral process. Petiole node in dorsal view very narrow, slightly expanded. Postpetiole in dorsal view much longer than broad. Basal portion of first gastral tergite constricted, forming a narrow neck behind the postpetiole. Dorsum of head with arched longitudinal costulae on the genae and frontal lobes, the costulae curving in towards the midline posteriorly. Remainder of dorsum to occipital margin densely transversely costulate. Ground-sculpture vestigial, merely a superficial patterning between the costulae. Sides of alitrunk strongly, regularly and sharply costulate everywhere, the dorsum similarly sculptured, as is thf: propodeal declivity. All dorsal sculpture transverse except between the mesothoracic spiracles. Petiole encircled by fine rugulae or costulae which are most strongly developed ventrally. Postpetiole and gaster unsculptured. All dorsal surfaces of head and body with scattered acute hairs of varying length; those on the first gastral tergite shorter and sparser than elsewhere. Colour dark dull red, the postpetiole and gaster lighter, yellowish.

Syntype Specimen Labels

Type Material

Bolton (1981) - Syntype workers, Somali Republic: Uebi (Robecchi), and Erdal (Pavesi) (Musee d'Histoire Naturelle Genève, Museo Civico di Storia Naturale, Genoa) [examined].

References

• 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. (page 276, see also)
• Bolton, B. and A. C. Marsh. 1989. The Afrotropical thermophilic ant genus Ocymyrmex (Hymenoptera: Formicidae). Journal of Natural History. 23:1267-1308.
• Emery, C. 1892b. Sopra alcune formiche raccolte dall'Ingegnere L. Bricchetti Robecchi nel paese dei Somali. [concl.]. Ann. Mus. Civ. Stor. Nat. 32[=(2(12): 113-122 (page 114, fig. worker described)
• Menozzi, C. 1922b. Miscellanea mirmecologica. [concl.]. Ann. Mus. Civ. Stor. Nat. "Giacomo Doria" 49[=(3)(9): 353-358 (page 353, male described)

References based on Global Ant Biodiversity Informatics

• 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.
• Bolton B., and A. C. Marsh. 1989. The Afrotropical thermophilic ant genus Ocymyrmex (Hymenoptera: Formicidae). Journal of Natural History 23: 1267-1308.
• Garcia F.H., Wiesel E. and Fischer G. 2013.The Ants of Kenya (Hymenoptera: Formicidae)—Faunal Overview, First Species Checklist, Bibliography, Accounts for All Genera, and Discussion on Taxonomy and Zoogeography. Journal of East African Natural History, 101(2): 127-222
• Menozzi C. 1930. Formiche della Somalia italiana meridionale. Memorie della Società Entomologica Italiana. 9: 76-130.
• Menozzi C. 1939. Hymenoptera Formicidae. Missione Biologica nel Paese dei Borana. 3: 97-110.
• Menozzi C., M. Consani. 1952. Missione biologica Sagan-Omo diretta dal Prof. E. Zavattari. Hymenoptera Formicidae. Rivista di Biologia Coloniale 11: 57-71.
• Santschi F. 1935. Hymenoptera. I. Formicidae. Mission Scientifique de l'Omo 2: 255-277.
• Wheeler W. M. 1922. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. VIII. A synonymic list of the ants of the Ethiopian region. Bulletin of the American Museum of Natural History 45: 711-1004