Taxonomy of the Myrmicine ant genus Temnothorax Mayr, 1861 (Formicidae: Myrmicinae) in the Arabian Peninsula

The Arabian Temnothorax Mayr, 1861 fauna is revised for the fi rst time. Three species are recognized from the region: Temnothorax arabicus Sharaf & Akbar sp. nov., T. liviae (Agosti & Collingwood, 2011) comb. nov. and T. megalops (Hamann & Klemm, 1967). Leptothorax saudiae Collingwood & Agosti, 1996 was placed in Temnothorax by Bolton (2003), but actually belongs to Tetramorium Mayr, 1855 and is herewithin recombined to Tetramorium saudiae (Collingwood & Agosti, 1996) comb. nov. Automontage images and comparative diagnoses of workers as well as notes on habitats and distribution of treated species are provided. A revised key to the Arabian species based on the worker caste is also presented.

The majority of species of Temnothorax are known to maintain small colony sizes often including less than 200-300 individuals. Several species of the genus have been reared under controlled laboratory conditions for studies on population growth (Buschinger 1968(Buschinger , 1974, colony structure, pronounced kin confl ict (Heinze 2004), social parasites, guest ants, slave-makers, workerless inquiline behavior (Buschinger 1981(Buschinger , 1986(Buschinger , 2009Hölldobler & Wilson 1990), and behavioral ecology (Aleksiev et al. 2007;Pratt et al. 2005;Dornhaus & Franks 2006;Franks & Richardson 2006;Basari et al. 2014). These ants have a wide habitat range and variety of feeding habits (Mackay 2000;Fokuhl et al. 2012). The use of light traps and the handpicking method during evening hours enhance opportunities for collection as these ants are mostly nocturnal and dusk foragers. Social parasitism is exhibited by several species of the genus. Diagnoses of the morphologically similar and sympatric genera Temnothorax, Nesomyrmex Wheeler, 1910, Leptothorax andTetramorium Mayr, 1855 are presented in detail by Bolton (1982), Radchenko (2004) and Prebus (2015).
In the Arabian Peninsula, Temnothorax has received relatively little attention. Only a few isolated descriptions have been published from the region. Collingwood & Agosti (1996) listed six taxa of Temnothorax occurring in the Arabian Peninsula and formerly assigned to the genus Leptothorax: L. humerosus (Emery, 1846), L. angulatus (Mayr, 1862) and L. saudiae (Collingwood & Agosti, 1996), plus three undescribed species (Leptothorax A, B, C). Bolton (2003) transferred L. humerosus and L. angulatus to the genus Nesomyrmex. Collingwood et al. (2011) described a new species, L. liviae, and reported L. megalops for the fi rst time from the UAE. The three undescribed species (Collingwood & Agosti 1996) were never established as valid species and cannot be found in the World Museum Liverpool Collection, Liverpool, United Kingdom (WMLC), where Collingwood's collection is deposited.

Material and methods
The material examined in this study was collected by pitfall traps, Malaise traps, and hand searching methods during surveys carried out in different regions of the Kingdom of Saudi Arabia (KSA) from 2010 to 2015. Type material of the treated species conserved in different museums (WMLC, KSMA, NHMB, NHMW, and CASC) was also studied and compared. Morphological examinations were conducted using a Nikon SMZ 1500 stereo zoom microscope. Digital color images of lateral and dorsal views of the entire body and full-face views of the head of each species were created using a Leica DFC450 digital camera with a Leica Z16 APO microscope and Leica Application Suite LAS (v3.8) software. These images are also available online on AntWeb (www.AntWeb.org) and are accessible using the unique identifying specimen code.

Abbreviations for morphological terms
Throughout the text, 'w' stands for 'worker' or 'workers' and 'q' for 'queen'.
All measurements are given in millimeters following Seifert (2006), Snelling et al. (2014)    prominent teeth. Mesosoma slender (WL 0.74-0.75); in profi le, mesosoma forming almost a continuous arch; metanotal groove weakly impressed; humeri in dorsal view rounded; propodeal spines long and sharp with acute tips (PSLI 33-35), slightly longer than distance between their bases; metafemur much longer than wide in dorsal view (HFL 0.61-0.62, HFW 0.11-0.12). Petiole node highest anteriorly, with a slightly concave anterior face and fl at dorsum, sloping downwards to the posterior face; subpetiolar process reduced. Postpetiole node rounded in profi le and trapezoidal in dorsal view. Gaster ovate, smooth and shiny; basal half of fi rst tergite slightly roughened, becoming increasingly shiny and weakly sculptured.
HEAD AND BODY. Uniformly pale brownish yellow to light brown, head and gaster slightly darker. Head, median lobe of clypeus and supraclypeal area, smooth and shiny; longitudinal rugae distinct over cephalic surface in full-face view; mesosoma weakly reticulate-rugolose. Petiole and postpetiole nodes dull and fi nely reticulate, without much rugae. Vertex, frons and frontal lobes with few erect hairs; clypeus with a single erect hair on each side of median lobe in addition to usual long curled hairs along anterior margin. Erect hairs also present throughout mesosoma; petiole and postpetiole with several erect hairs which are longer than mesosomal pilosity; all gastral tergites with scattered short, erect or suberect hairs.

Ecology
The holotype and a single paratype specimen were collected in a pitfall trap set in the Asir Mountains. Other paratype specimens were collected by sifting soil from litter samples taken under a palm tree Hyphaene thebaica (L.) Mart. (Arecaceae) in the provinces of Jizan and Al Bahah in Saudi Arabia.

Remarks
The new species is a member of the T. laurae (Prebus, 2015) species group of the Afrotropical Region. Among the poorly known species from the region, T. arabicus sp. nov. seems to have affi nities with T. mpala Prebus, 2015 from Kenya. The two species can be easily differentiated through a combination of characteristics. T. arabicus sp. nov. = head longer than broad (CI 79), lateral margins strongly converge anteriorly and posteriorly, smaller propodeal Spine Index (PSLI 33-35), clypeus smooth and shiny without any prominent median or longitudinal rugae, cephalic dorsum with feeble longitudinal rugae and pilosity prominent; whereas T. mpala = head subrectangular, longer than broad (CI 72-76), lateral sides parallel, slightly converging towards the mandibular insertions, higher propodeal Spine Index (PSLI 25-27), clypeus with strongly developed median ruga and much more prominent longitudinal rugae, cephalic dorsum reticulate, and pilosity sparse.
The two species differ considerably in morphometrics as well (in T. arabicus sp. nov., PTL 0.14-0.  HEAD. Distinctly longer than broad (CI 77), with straight posterior and lateral margins; eyes massive (EL 0.45 × HW), with 20 ommatidia in longest row; frontal carinae short extending back only as far as the anterior level of eyes; scapes relatively long (SI 119), when laid back from their insertions clearly surpassing posterior margin of head. Mesosoma slender (WL 1.16); metanotal groove shallow but distinct; propodeal dorsum nearly straight or feebly convex; propodeal spines long, sharp and acute (PSLI 34); anterior pronotal corners distinctly rounded in dorsal view. In profi le, petiole distinctly longer than broad (PI 49), with convex dorsum. Postpetiole distinctly broader than long.
BODY. Pale brown, gaster dark brown, antennae, mandibles and legs yellow. Cephalic dorsum strongly, longitudinally and irregularly striate; mandibles feebly longitudinally striate; mesosoma irregularly longitudinally striate; petiole and postpetiole feebly and superfi cially sculptured; gaster smooth and shining. Cephalic dorsum with many sparse short hairs; underside of head with a few short curved hairs; mesosomal pilosity restricted to three pairs on pronotal angles, two on mesonotum and two short pairs on propodeal dorsum; petiole with two pairs of long back directed hairs; postpetiole with three pairs of long hairs; gaster with many scattered shorter hairs. HEAD AND BODY. Similar to the workers from the same colony but larger, with thicker body, especially mesosoma and gaster. Ocelli present, prominent. Pilosity is much more prominent compared to the workers.

Ecology
Specimens were collected in a pitfall trap from Baynunah, a sandy desert in United Arab Emirates (UAE). The species is known only from its type locality.

Remarks
Despite the absence of formally published data, Leptothorax liviae has long been treated as a member of the genus Temnothorax (Bolton 2017). This generic placement of the species is obvious from the presence of a median clypeal carina, the absence of a transverse crest on the stipes, and the 12-segmented antennae, typical of Temnothorax. Based on Bolton's unpublished opinion and examination of the material during the present study, Leptothorax liviae is hereby validated as Temnothorax liviae (Agosti & Collingwood, 2011) comb.nov. (Hamann & Klemm, 1967) Figs 10-15

Remarks
The species was recently treated by Prebus (2015), who provided a complete diagnosis.

Species excluded from synonomy of Temnothorax
Tetramorium saudiae (Collingwood & Agosti, 1996) Collingwood & Agosti (1996) described Leptothorax saudiae based upon a single specimen deposited in WMLC. The specimen in WMLC with a red label [Saudi Arabien, Al Muraywah, 28 46N, 45 00E, 27-28 Oct. 86, 420 m, W. Buttiker] is not specifi ed as the holotype, yet the label information matches the original description exactly. This specimen, therefore, defi nitely represents the Leptothorax saudiae holotype. However, contrary to Bolton's transferral of the species to Temnothorax (Bolton 2003), this specimen clearly belongs to the genus Tetramorium based on the following observations: it possesses lateral portions of clypeus that are raised into sharp ridges or shield walls in front of the antennal insertions and the propodeal spiracles are low on the sides and distinctly behind the midlength of the sclerite. This taxon is herein formally transferred to the genus Tetramorium.

Discussion
The genus Temnothorax is represented by only three valid species from the Arabian Peninsula. These are T. arabicus sp. nov., T. liviae comb. nov., and T. megalops. These three species have been infrequently encountered in collections. Temnothorax liviae comb. nov. may be considered rarest among the known regional species, having been reported so far from its type locality only. The Temnothorax fauna of the Arabian Peninsula has its closest affi nity with the T. laurae species group from Iberia, North and East Africa. The group is characterized by an elongate head capsule, large eyes with distinct micropilosity between the facets (there is, however, no sign of such micropilosity on any of the AntWeb photographs of the species), trapezoidal petiole, coarsely striate sculpture and impressed metanotal groove (Cagniant & Espadaler 1997;Tinaut 1995;Prebus 2015).