Ants of the Genus Solenopsis Westwood 1840 (Hymenoptera: Formicidae) in the Arabian Peninsula with Description of a New Species, Solenopsis elhawagryi

Ants of the genus Solenopsis Westwood in the Arabian Peninsula are revised. Six species are treated: Solenopsis elhawagryi Sharaf & Aldawood sp. n., S. geminata (Fabricius, 1804), S. omana Collingwood & Agosti, 1996, S. saudiensis Sharaf & Aldawood, 2011, S. sumara Collingwood & Agosti, 1996, and S. zingibara Collingwood & Agosti, 1996. Solenopsis elhawagryi is described from Beljorashi Governorate, Al Baha Province, Saudi Arabia, based on worker castes and the queen with notes on this species biology and ecology. Solenopsis sumara workers are redescribed and illustrated for the first time and a lectotype is designated. An identification key to the Arabian and Egyptian species is provided with scanning electron micrographs to facilitate species recognition.


Introduction
This is the second contribution to the revision of the ant genera of the Arabian Peninsula (referred to hereafter as ''Arabia''). The first paper treated the genus Plagiolepis [1]. This revision concerns the genus Solenopsis as defined by Westwood [2] with the type species S. mandibularis Westwood. Often known as thief ants, globally this is one of the largest genera in the subfamily Myrmicinae, with more than 285 recognized taxa [3] distributed in tropical and warm temperate regions [4].
The Solenopsis character states follow the definitions of Ettershank [5] and Bolton [6]: members of the genus are monomorphic or polymorphic. The mandibles of Solenopsis species are tri or quadridentate; a palp formula of 2, 2 or 1, 2; the clypeus longitudinally bicarinate, with the median area sharply elevated and deeply inserted between the closely approximated frontal lobes; the anterior clypeal margin with a single long median seta; antennae ten-segmented with a two-segmented club; propodeum unarmed; petiole always distinctly pedunculate, node high and rounded.
Despite their abundance, few revisionary treatments have included Solenopsis. A global study of taxa related to Solenopsis and Pheidologeton Mayr listed 257 species [5]. New World species of the Solenopsis geminata-group were reviewed by Trager [7], who supported the synonymy of Bisolenopsis Kusnezov, Synsolenopsis Forel, Paranamyrma Kusnezov, and Labauchena Santschi, with Solenopsis. Recently, a comprehensive review of North American thief ants recognized eighty-three taxa including eleven new species [8].
The scarcity of published knowledge may be due to the difficult taxonomy of the genus when compared to other Formicidae and the small size of workers. Because of their small size, pale coloration, and cryptic habitats, the Arabian species may well have been overlooked by collectors. Perhaps the best expression of this situation is the statement of Creighton [9]: ''The student of North American ants may count himself fortunate that so few species of this difficult genus occur in our latitudes. He/she is thus saved from the task of trying to distinguish the many tropical species whose worker caste shows an astonishing and baffling convergence.'' The first and sole paper which treats Arabian Solenopsis is that of Collingwood & Agosti [10]. The genus was reported for the first time from Arabia where three new species are described including, Solenopsis omana from Oman and UAE, Solenopsis sumara and S. zingibara from Yemen. The descriptions, however, are relatively brief and only S. omana was illustrated.
A year later, the invasive pest, S. geminata (Fabricius) was recorded from UAE, where it was causing irritating nuisance to race horses and camels [11]. Recently, the genus was reported in Saudi Arabia (Riyadh), with a further new species, S. saudiensis, described and provided with ecological and biological notes [12]. The authors presented the first key to the known four Arabian species together with the four known Egyptian species, S. cooperi Donisthorpe, S. lou Forel, S. occipitalis Santschi, and S. kochi Finzi [13]. Solenopsis geminata was not included.
Here, the Solenopsis fauna of Arabia is reviewed. Solenopsis elhawagryi sp. n. is described and illustrated based on worker and queen castes and notes on its natural history are provided. Solenopsis sumara is redescribed, comprehensively measured, and illustrated for the first time, with designation of a lectotype. A key to the six recorded Arabian species with the four Egyptian species is presented to facilitate species regional recognition, although the type specimens of S. zingibara appear to be lost [Guy Knight, WMLC, Daniel Burkhardt, Isabelle Pfander, NHMB, personal communications] and the taxonomic treatment of this species is based on the original description.    All measurements are in millimeters and follow the standard measurements [14].

Measurements and indices
Specimens of Solenopsis were examined from the following collections: BMNH Natural History Museum, London, United Kingdom.
CACC CACC Cedric A. Collingwood Collection. The holotype specimen of the new species S. elhawagryi is deposited at KSMA and a single paratype specimen is deposited at all the later museums except TAUI. An official permission from KSMA and WMLC has been obtained to examine some type materials according to their loan policy.

Illustrations
Specimens were photographed by Erin Prado using a JVC KY-F70B 3CCD digital camera attached to a Leica M420 stereomicroscope. All digital images were processed using Auto-Montage (Syncroscopy, Division of Synoptics Ltd, USA) software. Images of the specimens are available in full color on www.antweb.org No specific permits were required for the described field studies or for the surveyed locations which are not privately-owned or protected in any way or do not have endangered or protected species. Solenopsis specimens were collected by sifting tray and aspirator in Elqamh Park, Al Baha Province, southwestern Saudi Arabia. Solenopsis saudiensis and S. sumara specimens were examined in collections at King Saud Museum of Arthropods (KSMA) and World Museum Liverpool (WMLC). Official permission from KSMA and WMLC was obtained to examine type materials according to museum loan policy.

Nomenclatural acts
The electronic edition of this article conforms to the requirements of the amended International Code of Zoological Nomenclature, and hence the new names contained herein are available under that Code from the electronic edition of this article. This published work and the nomenclatural acts it contains have been registered in ZooBank, the online registration system for the ICZN. The ZooBank LSIDs (Life Science Identifiers) can be resolved and the associated information viewed through any standard web browser by appending the LSID to the prefix ''http://zoobank.org/''. The LSID for this publication is: urn:lsid:zoobank.org:pub: [D3189D0E-ECAA-44E9-9CCE-9E2E7748AC42]. The electronic edition of this work was published in a journal with an ISSN, and has been archived and   is available from the following digital repositories: PubMed Central, LOCKSS.    Paratypes. 20 workers, same locality and data as holotype, 1 (MHNG ); 1 ( NHMB ); 1 (CASC); 1 (WMLC); 1 (BMNH) and 15 (KSMA). In addition, 35 paratype specimens preserved in alcohol, 8 major workers and 27 minors (KSMA).

Solenopsis elhawagryi
Diagnosis. Major workers can be easily separated from other Arabian Solenopsis by the color, head partially brownish yellow with the area in front of eyes yellowish and few scattered yellowish spots; posterior margin of first gastral tergite brownish. In addition, elhawagryi is similar to omana, both having the postpetiole with   anteroventral projection, but the former species can be readily recognized from the later by the number of ommatidia of eyes which is four-five whereas in omana, eyes have seven ommatidia.

Description
Major worker (Figs. [1][2][3][4][5][6][7][8][9]. Head clearly longer than broad with weakly convex sides and nearly straight or very feebly concave posterior margin; cephalic dorsum smooth and shining with abundant short pitted setae; eyes small and oval, with fourfive ommatidia; anterior clypeal margin with a central pair of stout projecting teeth and a lateral pair of short, broad basal blunt teeth; mandibles smooth and shiny, armed with four teeth, apical tooth largest followed by two subequal teeth, more widely separated, basal tooth smallest; antennae with terminal funicular segment long and about 3 times longer than proceeding segment; frontal carina much reduced. Metanotal groove a V-shape, with a narrow, acute cleft; propodeum outline a continuous curve in lateral view; propodeal spiracle circular. Petiolar peduncle with a small ventral tooth, high node and rounded dorsum, in dorsal view   and about twice as broad as long. Postpetiole profile high and slightly spherical, with a distinct anteroventral tooth-like process bearing few setae; dorsum with a weak, superficial alveolate pattern; pilosity of mesosoma, petiole, postpetiole and gaster relatively abundant and long. Coloration overall yellow; head partially brownish yellow with the area in front of eyes yellowish and few scattered yellowish spots; posterior margin of first gastral tergite brownish. Overall smooth and shining.
Minor worker (Figs. [10][11][12][13][14][15][16][17][18]. Most characters are as in the major workers but: head little longer than broad, with feebly convex sides; eyes proportionally smaller, with four ommatidia; central clypeal teeth widely separated, long, and acute; body pilosity shorter, especially on the head. Queen (alate) (Figs. [19][20][21]. Head distinctly longer than broad with slightly convex sides and a feebly concave posterior margin; cephalic dorsum smooth and brilliant with abundant inwardly-directed setae, central setae much longer; the three ocelli large and whitish; eyes very large (about 0.336 HW) with more than 25 ommatidia in the longest row; anterior clypeal margin with a central pair of stout projecting teeth, and a lateral pair of short, broad basal blunt teeth; mandibles faintly longitudinally striated, armed with four teeth, the distal one being the largest, and the second and third being subequal and slightly far apart; basal tooth the smallest; antennal scape short, just surpassing the level of posterior margin of eyes; frontal carinae much reduced. Mesosoma robust with abundant, short, suberect setae. Petiolar dorsum narrow and convex in profile. Postpetiolar dorsum wide and convex. Petiole and postpetiole have abundant, long, backwardly-directed setae and petiole with a small distinct anteroventral toothlike process which bears few long setae; both smooth and shining, with imbricate sculpture on sides. Gaster long and robust. Color uniformly dark brown, funiculus, distal half of scape, legs and mandibles yellowish, basal half of scape brownish yellow, mesopleura light brownish.
Affinities. Solenopsis elhawagryi appears closest to S. omana from Oman and UAE and S. dentata from Israel. All three species share the following characters: anterior clypeal margin with a central pair of stout projecting teeth and a lateral pair of short, broad basal blunt teeth; head longer than broad; petiole node high and rounded in profile, peduncle with a small ventral tooth, node from above distinctly broader than long; postpetiole in profile with a characteristic tooth-like anteroventral flange, with some projecting setae.
Solenopsis elhawagryi can be easily distinguished from S. dentata (type examined, Figs. 22-24) by the following characters: the postpetiolar tooth-like anteroventral flange is simple but distinct, whereas in dentata it is more acute, longer and clearly curved, and very characteristic; the eyes have four-five ommatidia while dentata has 7 ommatidia; the propodeal outline is a continuous curve in lateral view, whereas in dentata the propodeal dorsum meeting the declicity in an obtuse angle; elhawagryi has a characteristic Vshaped, narrow and acute metanotal groove, while the metanotal groove in dentata is less acute. In addition, elhawagryi has less abundant body pilosity while dentata has more abundant pilosity.  Moreover, elhawagryi has a lower scape index, SI 60-80 against SI 81-89; the cephalic index is slightly lower, CI 76-88 against CI 82-89.
Comparing the queen of elhawagryi and dentata, both are similar in color (dark brown or blackish brown) and body measurements, but consistent differences occur. The eyes of elhawagryi are distinctly larger (about 0.336 HW), with more than 25 ommatidia in the longest row, the dentata eyes are about 0.256 HW, with 18 ommatidia in the longest row; elhawagryi has a lower cephalic index, CI 87 versus CI 93-95, and a slightly higher scape index SI 72 versus SI 67-69.  Comparing elhawagryi with omana, the major worker eyes have four-five ommatidia, compared with seven ommatidia; elhawagryi has the head in profile appearing thick with a flat dorsal surface, and a distinctly convex ventral surface, while in omana the head in profile appears narrow with a flat ventral surface; the cephalic index tends to be larger, CI 76-88 versus CI 79-81.
Etymology. This new species is named in the honor of Prof. Magdi El-Hawagry (Cairo University and Al Baha University).
Habitat and Biology. The type locality is a forest called Elqamh Park, Beljorashi Governorate, Al Baha Province, Kingdom of Saudi Arabia, with many water pools, and soil has significant degree of humidity after heavy rainy season. The area has much native vegetation including: Acacia origena A. Hunde, Acacia negrri Pichi-Sermoli, Solanum sp., and Juniperus procera Hochst. Ex Endle. The type specimen was taken from a nest under a stone on loose soil next to a large and old Acacia tree, the nest contained tens of major and minor workers, and two alate queens. No additional nests were found despite extensive surveys in the area. In addition, we were unable to collect foraging workers near the nest. Several other ant species were found in the same habitat including: Crematogaster affabilis Forel, Monomorium mayri Forel, M. salomonis (L.), M. monomorium group, Tetramorium sericeiventre Emery, and Lepisiota obtusa Emery.
Although this new species has not been found in any area other than the type locality and despite intensive collecting efforts in the surrounding areas in Asir Mountains, it is not certain that this  Solenopsis geminata Mayr, 1863:453 [15]. Diagnosis. Solenopsis geminata can be distinguished from other Arabian species by the combination of the following characters: head subquadrate to subtrapezoidal; posterior margin of head with deep angular median emargination; mandibles thick and strongly curved mesad, especially in largest individuals; propodeal dorsum with distinct dorsolateral carinae; petiolar ventral process small.
Workers. Polymorphic; head subquadrate to subtrapezoidal, with straight to feebly convex sides and parallel to feebly divergent anteriad, often slightly indented just anterior to eyes; posterior margin of head with deep angular median emargination between nearly hemispherical lobes; eyes small relative to head, with 9-11 ommatidia in longest row; median clypeal tooth rudimentary; carinal teeth thick at base, strongly protruding; mandibles thick and strongly curved mesad, especially in largest individuals. Pronotal profile strongly convex and at most weakly angular; promesonotal suture distinct, approximately right-angular to weakly obtuse-angular; metanotal groove impressed; propodeal profile nearly diamond-shaped, with flat to weakly concave dorsum; propodeal dorsum of large and smaller workers with distinct dorsolateral carinae. . Cephalic and promesonotal pilosity abundant. Color very variable, from concolorous orange-red with only posterior margin of gaster dark brown, to nearly concolorous brownish black with only head near base of mandibles and appendages reddish-brown. Smaller workers darker and more uniformly colored than larger ones.  Queen. TL 7.5-8.0 mm [16] Head one-sixth broader than long, quadrate, little wider behind eyes than in front of them, sides very feebly convex from eyes to posterior corners of head, straight or nearly straight in front of eyes and meeting anterior border of head at sharp angle. posterior corners of head well-marked, posterior margin flat with narrow and shallow median impression, frontal furrow short, clearly marked only for about half distance from median ocellus to base of frontal lobes, thereafter becoming shallow and indistinct; ocelli large and prominent; clypeus feebly projecting, carinal teeth very stout, blunt, clypeal border between them with shallow concave impression; lateral denticles small, feebly defined; masticatory margin of mandibles with three large teeth and usually rudiment of fourth one; eyes large, strongly convex, irregularly oval in outline, posterior border reaching a point half way between posterior and anterior borders of head; antennal scape just reaches lateral ocellus; funicular segments and club as in major worker. Mesosoma robust, elliptical, maximum width three-fifths of its length, slightly narrower than head (eyes excluded); mesonotum in profile with straight posterior half and convex anterior portion overhangs pronotum; Scutellum as high as mesonotum, feebly convex with short, perpendicular posterior face; propodeal angle well-defined, obtuse, with propodeal dorsum and declivity of about equal length. Petiolar nodes similar to those of major worker except thicker peduncle, node of petiole slightly lower and postpetiole with obtuse, conical, ventral projection on sides. Seen from above, petiole and postpetiole strongly transverse and with equal width. Gaster as in major worker.
Male. TL 5.80 mm [16]. Head trapezoidal, maximum width (including eyes) approximately one-fourth greater than its length; eyes very large, strongly convex and oval in outline, occupying more than one-half head sides, their anterior border reaching mandibular insertions; ocelli very large and prominent, lateral  ocelli with shallow concave impression between them; anterior clypeal margin nearly straight; mandibles small, linear, bidentate; antennal scape about one and one-half times as long as broad, cylindrical; first funicular segment sub globose, broader than scape; second funicular segment more than twice as long as broad, third joint one and one-half times as long as broad, remaining segments more than twice as long as broad. Mesosoma elliptical, its greatest width two-thirds of its length; anterior part of mesonotum in profile greatly swollen and overhangs pronotum; propodeum slightly rounded, basal face strongly convex transversely and slightly convex longitudinally, declivity flat, virtually perpendicular. Petiolar node in profile low but with acute summit, anterior face not sharply separated from thick peduncle, posterior face perpendicular; summit of node from posterior view with broad, shallow median impression. Postpetiole in profile as high as node of petiole, about one and one-half times as high as long with long, backward sloping anterior face; postpetiole nearly three times as broad as long. First gastral segment truncate at base but not impressed.

Distribution.
A species endemic to Central American that has spread through commerce to many countries [17][18][19]. It was collected for the first time in Arabia from Dubai [11] where it was an irritating nuisance to racing horses and camels. Diagnosis. This species is closest related to elhawagryi, but is quickly separated by the eyes which having seven ommatidia whereas eyes of elhawagryi with four-five ommatidia.

Solenopsis omana
Description of major worker. Head subrectangular in dorsal view, narrow with a flat ventral surface in profile, with nearly straight posterior margin and feebly convex sides; eyes with seven ommatidia; central clypeal teeth widely spaced, short and blunt; teeth at each side very small projections. Metanotal groove deep and making an acute angle in profile; propodeal dorsum about 1.56 longer than propodeal declivity. Petiolar node higher than postpetiolar node; postpetiole with an anteroventral small projecting teeth in profile; All body surfaces with long setae which appear as a fringe surrounding posterior margin of head and genae; head smooth and shining with scattered large punctures, rest of body faintly sculptured or unsculptured; color dirty yellow, head and first gastral tergite with yellow brownish tint.
Remarks. Collingwood and Agosti [10] did not mention whether the described caste was a major or minor worker, but the measurements and the short, blunt, widely separated central clypeal teeth are shared by major workers of its congener, S. elhawagryi. The color also was not stated although they compare it to the yellow S. orbula. That, however, has minute eyes and sharp clypeal teeth. The original paper (p. 301) stated all type material was deposited in the NHMB but no specimens denoted as types   Diagnosis. Among Solenopsis species of the Arabian Peninsula, S. saudiensis is the only monomorphic species and can be immediately distinguished by its smaller size, TL 1.2-1.3 mm.
Description of worker. Head longer than broad in full face view; head dorsum smooth and shining with abundant scattered minute hair pits; eyes of two minute dark ommatidia; clypeus with a strongly impressed anterior margin and sharp carinae; anterior margin with a central pair of stout projecting teeth (0.02 mm), and  a lateral pair of short, broad basal blunt teeth; mandibles with four reddish brown teeth, apical tooth is the largest, basal one is the smallest, second and third teeth subequal; antennae ten-segmented with a well-defined two-segmented club; scape fails to reach posterior margin of head; funicular segments two-seven about twice broader than long, with abundant, decumbent long yellow setae. Promesonotum with a smooth and uninterrupted profile; metanotal groove weakly but distinctly impressed; impression between mesopleuron and metapleuron faintly striate; propodeum short and low, with basal face making a continuous arc with the declivity, and a shallow dorsal longitudinal impression; spiracle is relatively large (0.02 mm diameter) and circular. Petiole as long as broad in dorsal view, in lateral view petiolar node high or slightly pointed; anterior peduncle with a distinct small ventral concave surface. Postpetiole about 1.36 broader than long; in profile node nearly hexagonal with a distinctly convex dorsal surface. All body parts are clothed with abundant, scattered, and moderately long yellow setae; cephalic pilosity short. Overall color uniform yellow.    Type. Lecotype major worker, same data of the type locality (WMLC).
Diagnosis. Solenopsis sumara is readily distinguished from its relative zingibara by the following characters: head subrectangular; frons without frontal striae; eyes tiny, with two ommatidia; petiolar node in profile massive, high and rounded, in dorsal view clearly broader than long.
Redescription of major worker. Head subrectangular with nearly parallel sides and narrower anteriorly than posteriorly and slightly but distinctly concave posterior margin; smooth and shining but with widely-spaced punctures; eyes minute, oval with two ommatidia, an upper larger one and a much smaller lower one (originally described as with two-three ommatidia); central clypeal teeth quite prominent and incurved with lateral teeth easily visible in full-face view (originally stated as hardly visible in dorsal view). Promesonotum flat; metanotal groove deep; basal face of propodeum forms a continuous curve with the declivity, which is much longer; spiracle circular. Petiole in profile with a massive and high rounded node and in dorsal view clearly broader than long or scarcely as long as broad; with a short peduncle. Postpetiole little broader than long or as long as broad, with node feebly convex or  nearly flat. Pilosity abundant on the head but scarce on pronotum, mesonotum and gaster; propodeum bare or has only one pair of seta. Setae of scape slightly longer than maximum width of scape. Unicolorous dirty yellowish or yellowish brown, with lateral clypeal margins and mandibular teeth reddish yellow. General appearance smooth and shining.
Remarks. In the original description Collingwood and Agosti listed only three specimens, the holotype and two paratypes but no clearly labeled holotype could be found in WMLC and only two specimens with red labels [Sumara Pass, 7.iii.1993, 2800 m] are exist without clear mentioning they are paratypes. It is highly unlikely, that the authors collected exactly two workers for the species, and not more. To prove that we looked for any type materials in the alcohol preserved collection in WMLC and a small tube with six specimens that has the same type locality data was found. The mentioned tube has been identified by Cedric Collingwood (pers. comm.) as containing the type materials, therefore, we believe that the original type series is in existence. We designate a lecotype in this study to unequivocally ascertain the identity of the species Solenopsis sumara. Queens and males are unknown. Diagnosis. Solenopsis zingibara is similar to S. sumara, both are the only yellowish brown species but the former can be readily recognized from the later by the following characters: head square; frons with six strong frontal striae; and eyes consist of three-four ommatidia; whereas sumara has a subrectangular head, frons without frontal striae; and eyes with only two ommatidia.

Discussion
Little is known about habitat and biology of Palaearctic and Arabian Solenopsis. Workers seem to build nests in the ground, sand mounds, and litter [4]. Some nest under stones, e g. S. sumara, S. dentata and S. elhawagryi. Or such as S. cooperi on Saloga and Ghazal islands in Nile River (Aswan, Egypt), nest in loose sandy soil close to bases of dead trees [13]. Solenopsis saudiensis nests under date palms, among decaying dropped fruit, directly under rocks or even inside discarded carpet. The latter species often coexists with Tapinoma simrothi Krausse that attends mealybugs [12]. Solenopis geminata is known to nest in open sunny areas of disturbed agricultural landscapes and around buildings, where nest mounds are defended aggressively by workers [7].
It appears that the Solenopsis in the Arabia is restricted to mid and lower elevations, usually below ca. 600 m. Despite repeated ant collections, there are only two records from the mountainous regions of southwestern Saudi Arabia and nearby Yemen. [10] reported S. sumara from Yemen, at 2500 m and, here, we report the new species S. elhawagryi. In Egypt, no Solenopsis were found in over 25 field trips to the high mountains of Sinai.
We hope our new descriptions and this revision will provide a foundation for future research into phylogeny, behavior, ecology, ecosystem structure and function, as well as systematic analyses of this fascinating, a seemingly important group of ants.