Eremomidas arabicus Bequaert, 1961

Dikow, T., 2010, Order Diptera, family Mydidae, Arthropod Fauna of the United Arab Emirates 3, Abu Dhabi: Dar Al Ummah, pp. 608-615 : 608-611

Eremomidas arabicus Bequaert, 1961

Plate 1

Diagnosis: E. arabicus is distinguished from other Eremomidas species by the overall white or light grey appearance (Plate 1), the sharply depressed vertex, the absence of long setae on thorax and abdomen, the vestigial proboscis, and M 1 + 2 terminating in R 1. To this day, it is the largest species of Mydidae found in the Arabian Peninsula, with females having a wing length of 17.5 - 18.2 mm.

Expanded diagnosis based on specimens studied:

Male. Head distinctly wider than thorax (at postpronotal lobes); interocular distance on vertex smaller than at ventral eye margin; vertex sharply depressed (nearly 90 ˚ angle on median eye margin); width of parafacial area (between tentorial pit and median eye margin) less than half the width of facial gibbosity (at same level); densely white pruinose, only ocellar triangle, vertex, and postgenae apruinose and dark brown; facial gibbosity distinct, discernible in lateral view, entirely covered with long, white mystacal setae; frons, vertex, and occiput with white setae; proboscis light brown, vestigial, knob-like; maxillary palpi laterally compressed, light brown, slightly longer than proboscis. Antennae brown; scape and pedicel with white setae dorsally and ventrally, scape longer than pedicel; postpedicel in proximal half cylindrical, distal half symmetrically bulbous,> 2.0 times as long as combined length of scape and pedicel; apical ‘seta-like’ sensory element situated apically in cavity on postpedicel.

Thorax. Light brown, predominantly white pruinose, only postpronotal lobes, proepisternum, anterior half of anepimeron, and posterior half of scutellum apruinose; scutum with faint dark grey longitudinal stripes just lateral of median line and laterally with presutural and postsutural spots. Setation. Distinct notopleural, supra-alar, and postalar macrosetae absent; white setae scattered on scutum, but not on faint dark grey spots / stripes, longest laterally dorsal to anepisternum; antepronotum, proepisternum, and postpronotal lobes with long white setae; katatergite and apruinose part of anepimeron with short white setae; scutellum, mesopostnotum, and anatergite asetose. Legs light brown to brown with white setae; pro and mes coxae apruinose, met coxae white pruinose; femora brown, met femora cylindrical as wide as pro and mes femora, met femora without ventral macrosetae; pro and mes tibiae laterally arched, met tibia straight, met tibia without ventral keel; pro and mes tarsomeres of equal length, met proximal tarsomere as long as combined length of 2 nd and 3 rd tarsomeres; pulvilli well-developed, as long as well-developed claws, much wider than base of claws. Wings. Length 11.2 - 11.4 mm; hyaline throughout, very few microtrichia scattered on wing, all veins light yellow, all marginal wing cells closed; C terminating at junction with R 1; R 4 either terminating in R 2 + 3 or R 1; R 5 terminating in R 1; stump vein (R 3) present at base of R 4; R 4 and R 5 (forming cell r 4) more or less parallel medially; M 1 + 2 terminating in R 1; CuA 1 and CuA 2 split proximally to m-cu (cell m 3 narrow proximally); alula very large, touching scutellum medially; haltere light yellow.

Abdomen. Predominantly brown, T 2 as wide as T 1, T white pruinose, S predominantly apruinose, scattered white setae; T 1 - 7 well-developed and visible; T 2 with anterior apruinose stripe; T 1 - 6 posterior margin yellow; bullae on T 2 light brown and circular; S 1 entirely yellow, S 2 - 7 posterior margin yellow. Terminalia not studied in detail.

Female. Interocular distance on vertex nearly as wide as width of base of scutellum (nearly 3 times as wide as in male) width of parafacial area (between tentorial pit and median eye margin) more than half the width of facial gibbosity; head setation much shorter, only few mystacal setae; thoracic setation much shorter; pulvilli on all tarsi about half the length of claws, only as wide as base of claws; wing length 17.5 - 18.2 mm; abdominal pruinosity reduced, only T 1 completely white pruinose, T 2 - 3 (slightly on T 4) only laterally pruinose, T 5 - 8 entirely apruinose; tergites proximally brown in varying extent. Genitalia. Ovipositor with acanthophorite plates each with 7 spurs; internal structures not studied.

Remarks: This species was described by Bequaert (1961: 33) from Seivun (= Say’un, Saiwun, 15 ° 56 ' N 48 ° 47 ' E) in central Yemen and is here recorded for the first time from Oman and the UAE. The holotype is deposited in the BMNH. This species shows sexual dimorphism particularly in the morphology of the head, the reduction of pulvilli in the female, and reduced setation in the female. Males and females of this species have been photographed at Khor Yfrah, Um al-Quwain, UAE, and the images have been published in Howarth (2006: Figs 1 - 2).

The placement of this species in Eremomidas is somewhat questionable based on comparison with Eremomidas bek Semenov, 1922 , from Kazakhstan. In particular, the shape of the aedeagus is different in that it is more or less dorso-ventrally flattened and not laterally compressed as in Eremomidas (see illustrations in Richter & Ovtshinnikova, 1996; Richter, 1997), the wing venation is more similar to Syllegomydinae in that M 1 + 2 terminates in R 1 and not in C as is found in Eremomidas and Leptomydinae , and the proboscis is vestigial as is always found in species of SyllegomydasBecker, 1906 ( Syllegomydinae ). The latter two characters are probably the reason why Deeming (2007) recorded a specimen from Oman (Wahiba Sands, NMWC) as belonging to Syllegomydas , which has now been identified as Eremomidas arabicus . The correct generic placement of this species and an undescribed one from Sudan, which is very similar in aedeagal and proboscis morphology and wing venation (unpublished data), needs to be established with a phylogenetic analysis of Mydidae genera that is currently in preparation by the author.

Distribution: Yemen, Oman, UAE. This species is therefore distributed in both the Afrotropical and Palaearctic regions.