Aenictus arabicus

This species, the only Aenictus known from Saudi Arabia, has been collected only once.

Identification
Sharaf & Aldawood (2012) - Aenictus arabicus is similar to Aenictus rhodiensis from Greece; and Aenictus sagei and Aenictus wroughtonii from India. All the three species are members of the wroughtonii group as defined by Jaitrong et al. (2010) and sharing the following characters: head narrow, entirely smooth and shining; occipital margin lacking collar; antennae long, 10-segmented; anterior clypeal margin convex, rounded, with 5–10 denticles; mandibles subtriangular, with masticatory margin bearing 8–12 minute teeth in addition to a large apical tooth with a sharpe apex; mesosoma narrow and elongate; subpetiolar process weakly developed or almost absent; body clear yellow to yellowish brown.

Comparing A. arabicus with A. rhodiensis, both species have a similar general morphology, notably the shape of the mesosoma, petiole and postpetiole, a similar body pilosity; also both have a peculiar subpetiolar process which is somewhat wide and blunt anteriorly and the anterior clypeal margin is equipped with six small denticles. From the more accurate description in Aktaç et al. (2004), A. arabicus can be separated readily from A. rhodiensis. The former has a small relatively long, narrow head (HL 0.60-0.72, HW 0.42-0.55, CI 70-92) and long scapes, when laid back surpassing about two-thirds of the head length (SI 77-104) while the latter has a shorter head (HL 1.23, HW 1.02) and shorter scapes, which just surpass the midpoint of the head. Aenictus arabicus has a nearly straight posterior margin of the head whereas it is weakly concave in A. rhodiensis. The funicular segments 2-8 are at least twice as long as broad in the former, while they are as long as broad in the latter. Aenictus arabicus has an entirely yellow clypeus and reddish-brown mandibular teeth while the sides of the clypeus and mandibular teeth are reddish brown in A. rhodiensis. The gaster of A. arabicus is entirely yellow, whereas in A. rhodiensis, the middle of the third gastral tergite has two longitudinal brownish lines which diverge forward, sometimes reducing to small points. Aenictus dlusskyi, known only from the type series from Armenia, also resembles A. arabicus but is of a similar size to rhodiensis (Aktaç et al. 2004).

Comparing A. arabicus with the Asian species A. sagei (CASENT0281958) and A. wroughtonii (lectotype images are given in Jaitrong et al. 2010: 35), A. arabicus has the anterior clypeal margin bearing six small denticles; A. sagei has 9-10 denticles; whereas A. wroughtonii has 8-10 denticles. In addition, A. arabicus has the subpetiolar process well developed, triangular, with convex ventral margin and blunt anteriorly and body pilosity fewer and shorter; A. sagei has a weakly developed subpetiolar process, with its ventral outline nearly straight; its anteroventral corners obtusely angulate and body pilosity distinctly long and abundant (length of the longest pronotal hair 0.20–0.25 mm, Jaitrong et al. 2010); whereas A. wroughtonii has an undeveloped subpetiolar process, with its ventral outline feebly convex and without anterior angle and relatively sparse standing hairs which are shorter than in A. sagei.

Distribution based on Regional Taxon Lists
Afrotropical Region: Saudi Arabia.

Biology


Al-Baha Province is divided by massive and steep rocky mountains into the lowland coastal plain to the west, known as “Tihama”, and the mountainous area ranging 1500- 2450 m above sea level to the east, known as “Al-Sarat or Al-Sarah” which forms part of Al-Sarawat Mountains. The type locality is a small farm at the beginning of a narrow valley isolated between the mountains and the plain at 1300m. A few native shrubs and trees are present, along with numerous cultivated crops. Aenictus arabicus was discovered foraging on the ground under leaf litter, next to a tree of Psidium guajava L. The soil contained some accumulated organic matter and at the time of collection was well saturated through irrigation.

In Tihama, the climate is hot in summer, warm in spring and mild in winter, with humidity ranging between 52%–67%, and rainfall less than 100 mm annually. While in the mountainous area, Al-Sarah, The climate is greatly different from that in Tihama although they are separated by no more than 30 km. The weather is cooler in summer and winter due to its high altitude. The topography in Al-Sarah can support the formation of clouds and fog. These often occur in winter due to air masses from the Red Sea and they may produce thunderstorms. In spring and summer, the climate is mild and pleasant. Also, rainfall is higher with falls in the range of 229–581 mm. The average rain falls throughout the whole province is 100–250 mm annually.

This is only the second record of Aenictus reported from the Arabian Peninsula. It follows a Collingwood and van Harten (2001) collection of workers of an identified species from Yemen that were found among the leaf litter of banana plantations in Khamis Bani Sa’d and Lahj.

The presence of an Aenictus species in the Southwestern part of Saudi Arabia is not surprising as the area is regarded as being Afrotropical (Bodenheimer 1937; Nayman 1972; Sharaf et al. 2012; El-Hawagry et al. unpubl. data), and it is likely that more Afrotropical ants are awaiting discovery in the area.

Castes
Known only from the worker caste.

Nomenclature

 * . Aenictus arabicus Sharaf & Aldawood, in Sharaf, Aldawood & El Hawagry, 2012b: 42, figs. 1-12 (w.) SAUDI ARABIA.
 * Status as species: Borowiec, L. 2014: 7; Jaitrong & Ruangsittichai, 2018: 113 (in key).

Worker
Holotype: TL 3.0, HL 0.65, HW 0.52, SL 0.50, PRW 0.35, ML 0.95, PL 0.22, PW 0.15, PPL 0.17, PPW 0.15. Indices: SI 96, CI 80.

Paratypes. TL 2.75-3.12, HL 0.60-0.72, HW 0.42-0.55, SL 0.40-0.52, PRW 0.20-0.35, ML 0.77-1.00, PL 0.22-0.27, PW 0.12-0.15, PPL 0.15-0.20, PPW 0.12-0.17. Indices: SI 77-104, CI 70-92. (n=11).

Head entirely smooth and shining. In full-face view head distinctly longer than broad, with convex sides and nearly straight posterior margin; occipital corners in lateral view rounded; anterior clypeal margin with six small denticles; masticatory margin of mandibles armed with a large apical tooth followed by five smaller subequal teeth and a relatively larger basal tooth; when laid back, antennal scapes surpassing about two thirds of head length; all funicular segments at least twice as long as broad; terminal funicular segment about 2.5 × as long as the proceeding segment; mandibles dull with longitudinal striations; whole head dorsum and antennae with stiff scattered long hairs. Mesosoma in dorsal view broader anteriorly than posteriorly; promesonotum in profile distinctly convex, bearing many pairs of hairs; metanotal groove distinct; mesopleuron faintly but distinctly imbricate; propodeum bare or in some individuals with very sparse decumbent pubescence; propodeal dorsum long, about 4× as long as declivity; propodeum in profile slightly lower than promesonotum and almost flat dorsally; propodeal junction rounded. Petiole longer than broad in dorsal view with node clearly convex in lateral view; subpetiolar process triangular with convex ventral margin and blunt anteriorly. Postpetiole distinctly smaller than petiole, its node roundly convex, and its anteroventral edge sharp and bearing many hairs; both petiole and postpetiole distinctly imbricate and equipped dorsally with several pairs of backward directed long hairs. Gaster smooth and shining with abundant pairs of hairs. Color uniformly yellow.

Type Material


The type locality is a small farm at the beginning of a narrow valley isolated between the mountains and the plain with a few native shrubs and trees at 1300 m. The farm is planted with Annona squamosa L. (Annonaceae), Prunus persica (L.), P. amigdalus (Mill.) (Rosaceae), Psidium guajava L. (Family: Myrtaceae), Zea mays ssp. mays L. (Family: Poaceae), in addition to banana, and mango. The species was found foraging on the ground under leaf litter and next to a tree of Psidium guajava L. The soil, at the time of collection was well saturated through irrigation and accumulation of organic matter.

Etymology
This species is named after the type locality.

References based on Global Ant Biodiversity Informatics

 * Borowiec M. L. 2016. Generic revision of the ant subfamily Dorylinae (Hymenoptera, Formicidae). ZooKeys 608: 1–280.
 * El-Hawagry M. S., M. W. Khalil, M. R. Sharaf, H. H. Fadl, and A. S. Aldawood. 2013. A preliminary study on the insect fauna of Al-Baha Province, Saudi Arabia, with descriptions of two new species. ZooKeys 274: 188. doi:10.3897/zookeys.274.4530
 * Sharaf M. R., H. M. Al Dhafer, and S. A. Aldawood. 2014. First record of the myrmicine ant genus Meranoplus Smith, 1853 (Hymenoptera: Formicidae) from the Arabian Peninsula with description of a new species and notes on the zoogeography of Southwestern Kingdom Saudi Arabia. PLoS ONE 9(11): e111298 (doi:10.1371/journal.pone.0111298).
 * Sharaf M. R., S. A. Aldawood, M. S. El-Hawagry. 2012. First record of the ant subfamily Aenictinae (Hymenoptera, Formicidae) from Saudi Arabia, with the description of a new species. ZooKeys 228: 39-49.