Monomorium moathi sp. n. is described and illustrated from Yemen based on the worker caste. This species belongs to the Monomorium salomonis-group, with closest resemblance to M. areniphilum Santschi, 1911. It is distinguished from the latter species by the following characters: Eyes oval, relatively large with eleven ommatidia in the longest row; Petiole node high and pointed in profile; Head, mesosoma and waist distinctly shagreenate granulate. Gaster finely shagreenate. Head dorsum, mesosoma, petiole, postpetiole and gastral tergites without hairs.
Keywords: Arabia, Palaearctic, Saudi Arabia, Myrmicinae, salomonis group, Taxonomy.
Monomorium was established by Mayr in 1855 by the type species Monomorium minutum Mayr, 1855 (later, given the new name Monomorium monomorium Bolton (1987:287). This genus includes 296 species and subspecies (Bolton, 1995) distributed in all zoogeographical regions, but the majority of species occur in the Old World tropics and warm temperate regions (Brown, 2000). Most species nest in rotten woods, under rocks or directly on earth.
Within the subfamily Myrmicinae, workers of the genus Monomorium are easily recognized by the combination of the following characters: Monomorphic to polymorphic ants, mandibles with 3-5 teeth which decrease in size from apex to base. Median portion of clypeus raised, the raised section longitudinally bicarinate. Frontal carinae absent behind frontal lobe. Antennal scrobes absent. Antennae 10-12 segmented but most frequently 12, usually with a conspicuous 3-segmented club. Eyes present but sometimes reduced to a single ommatidium as in the fossulatum-group. Metanotal groove present. Propodeal dorsum usually unarmed and rounding into the declivity. Petiole pedunculate anteriorly with a small anteroventral process.
The M. salomonis group (Bolton, 1987) is distinguished from other Monomorium species-groups by the following characters: Monomorphic with some size variation in any series. Palp formula 2,2. mandibles sculptured. Masticatory margin of mandibles with 4 teeth. Eyes distinct and moderate to large in size, circular to roughly oval, with 6 or more ommatidia in the longest row. Head always longer than broad. Scapes usually relatively large. Metanotal groove moderately impressed to absent. Propodeal dorsum usually sculptured but never transversely striate. Alitrunk, petiole and postpetiole usually conspicuously sculptured.
The ant fauna of the genus Monomorium in Yemen consists of 23 species scattered in Collingwood (1985), Collingwood & Van Harten (1994), Collingwood & Agosti (1996), Collingwood & Van Harten (2001), and Collingwood et al. (2004); 11 of them being described as new. In spite of these studies, species of that genus in Yemen are still inadequately known. In fact, this low number of Monomorium species in Yemen does not reflect the real number actually present as Yemen is considered one of the most poorly collected countries...