Introduction

The ant genus Carebara Westwood, 1840, sensuFernández (2004), is one of the largest ant genera of subfamily Myrmicinae with more than 180 species (Bolton et al. 2006) distributed worldwide in the tropics (Brown 2000) and the Afrotropical region (Weber 1950). Many of them are very tiny cryptic soil and leaf litter inhabitants (Longino 2004). They nest in rotten wood to which the bark is still adherent in the Afrotropical region (Bolton 1973), or may be lestobiotic (Longino 2004) nesting near other ant species. Little is known about the biology of the species.

The taxonomic knowledge also is limited. Fernández (2004) is the most comprehensive study but that dealt primarily with American species. He proposed a significant change to the systematics, however, in arguing for the combination of several genera under the single genus Carebara. Thus: Carebara Westwood, 1840; = Oligomyrmex Mayr, 1867 = Aeromyrma Forel, 1891; = Aneleus Emery, 1900; = Erebomyrma Wheeler, 1903; = Paedalgus Forel, 1911; = Lecanomyrma Forel, 1913; = Spelaeomyrmex Wheeler, 1922; = Hendecatella Wheeler, 1927; = Solenops Karawajew, 1930; = Sporocleptes Arnold, 1948; = Crateropsis Patrizi, 1948; = Nimbamyrma Bernard, 1953; = Afroxyidris Belshaw & Bolton, 1994 (provisional); = Neoblepharidatta Sheela & Narendran, 1997. Fernández (2010) has added Parvimyrma Eguchi & Bui, 2007 to the synonymy.

There are anomalies, however, in the Fernández proposal which was based primarily on the American fauna. In particular, it does not gel with the contrasting dimorphism of the Oligomyrmex workers, with minors, ca. 1.0 mm in total length (TL), and majors, TL ca. 2.0–2.5 mm, coupled, where known, with queens of a similar general morphology to the major workers and no more than twice as long, TL ca. 5–6 mm or less and the Carebara s.s. which have monomorphic workers with TL ca. 2.0 mm and grossly enlarged queens, most with TL 15 mm plus. The Carebara s.s. queens also are morphologically greatly dissimilar to any Oligomyrmex queens.

The genus Carebara sensuFernández (2004) was unknown from Arabia prior to the description of Carebara arabica (= Oligomyrmex arabicus) from Yemen by Collingwood and Van Harten 2001). Although the description of Carebara arabica might have been more explicit, it was based on major and minor workers, with drawings of both. Here, we give the first record of a Carebara species from Saudi Arabia based on the new species, Carebara abuhurayri.

Measurements and indices

Measurements in mm and indices are as follows (Bolton 1987):

TL Total Length; the outstretched length of the ant from the mandibular apex to the gastral apex.

HW Head Width; the maximum width of the head behind eyes in full face view.

HL Head Length; the maximum length of the head, excluding the mandibles.

CI Cephalic Index (HW x 100/HL).

SL Scape Length, excluding basal neck.

SI Scape Index (SL x 100/HW).

EL Eye Length; the maximum diameter of the eye.

ML Mesosoma Length; the length of the mesosoma (or alitrunk) in lateral view, from the point at which the pronotum meets the cervical shield to the posterior base of the propodeal lobes or teeth.

PRW Pronotal width in dorsal view.

PL Petiole Length; the maximum length measured in dorsal view, from the anterior margin to the posterior margin.

PW Petiole Width; maximum width measured in dorsal view.

PPL Postpetiole Length; maximum length measured in dorsal view.

PPW Postpetiole Width; maximum width measured in dorsal view.

Taxonomy Discussion Additional Arabian species

Carebara arabica (Collingwood & van Harten, 2001) which was described as Oligomyrmex arabicus from Yemen based on major and minor workers, and is known only from a single collection, is an example of a long-headed species with 11-segmented antennae (in the original description, the SL for major is given wrongly as 0.63, from the illustration it would be ca 0.16). The small worker of the new species Carebara abuhurayri appears not too dissimilar to the minor worker of Carebara arabica but it is consistently smaller in size (TL 0.99–1.13 mm versus TL 1.30); has a higher cephalic index (CI 74–89 versus CI 71), and a relatively lower head length (HL 0.35–0.41 versus HL 0.42). In addition, Carebara abuhurayri has a distinct but shallow metanotal groove compared with the deep groove in Carebara arabica. It does not resemble Carebara afghanus Pisarski, 1990, which has 9-segmented antennae but has a low, elongated and flat alitrunk profile without propodeal spines. The presence of single facet eyes, however, is the main characteristic, that sets Carebara abuhurayri apart from some of the African Carebara.

In pre-Fernández taxonomy Carebara abuhurayri might fall in the Oligomyrmex subgenus Aeromyrma, i.e. those with 10-segmented antennae. The only sub-Saharan species with 4-toothed mandibles is Oligomyrmex jeanneli Santschi, 1913. This has minor, TL 0.9 mm; metanotal groove shallow, dorsum of propodeum short; petiole noticeably narrower than postpetiole, postpetiole wider than long; head smooth, feebly punctuate, shiny; eyes atrophied set at anterior third of side; scape reaches posterior third of the head; petiole wider than high; postpetiole transverse, twice as wide as long; promesonotum wider than long; dorsum of propodeum wider than long unarmed; yellow, smooth and shiny.