Rhopalia olivieri Macquart, 1838

Dikow, T., 2010, Order Diptera, family Mydidae, Arthropod Fauna of the United Arab Emirates 3, Abu Dhabi: Dar Al Ummah, pp. 608-615 : 612-614

Rhopalia olivieri Macquart, 1838 Plates 2 - 3

Diagnosis: R. olivieri is a relatively small Mydidae species that is black and yellow in colouration (Plates 2 - 3) and can therefore be distinguished from other Mydidae in the Arabian Peninsula very easily. The well-developed proboscis distinguishes it from species of Perissocerus while the absence of colouration along the wing veins, in particular on veins M 1 + 2 and CuA 1, and the absence of CuA 1 + M 3 reaching the posterior wing margin distinguish it from Rhopalia gyps .

Expanded diagnosis based on specimens studied:

Male. Head distinctly wider than thorax (at postpronotal lobes); interocular distance on vertex greater than at ventral eye margin; vertex only slightly depressed; width of parafacial area (between tentorial pit and median eye margin) less than half the width of facial gibbosity (at same level); lateral face and occiput grey pruinose; facial gibbosity, ocellar triangle, frons, and vertex apruinose and dark brown; facial gibbosity distinct, well-developed and distinct in lateral view, entirely covered with long, white mystacal setae; facial gibbosity, frons, vertex, and postgenae with long white setae; occiput with short white setae; proboscis brown, well- developed, protruding well beyond apex of pedicel; maxillary palpi vestigial, cylindrical, light brown. Antennae brown; antennae elevated above eye margin in lateral view on distinct protuberance; scape and pedicel with yellow setae dorsally and ventrally, scape about 3 times as long as pedicel; postpedicel in proximal half cylindrical, distal half bulbous, expanded ventrally,> 7.0 times as long as combined length of scape and pedicel; apical ‘seta-like’ sensory element situated apically in cavity on postpedicel.

Thorax. Dark brown to black, predominantly apruinose, only antepronotum, proepimeron, katatergite, anatergite, and mesopostnotum grey pruinose; scutum predominantly black, postpronotal lobes and lateral scutum yellow. Setation. Distinct notopleural, supra-alar, and postalar macrosetae absent; long white setae scattered on scutum, postsutural dorsocentral setae directed anteriorly; proepimeron, lateral proepisternum, and anepimeron with long white setae; scutellum brown, laterally black, few white discal scutellar setae. Legs yellow with yellow setae; coxae partly brown, apruinose; femora yellow, met femora bulbous apically, evenly expanded, two rows of ventral macrosetae; pro and mes tibiae laterally arched, met tibia straight, met tibia without ventral keel; all proximal tarsomeres as long as 2 nd tarsomeres; pulvilli well-developed, about 3 / 4 of length of well-developed claws, much wider than base of claws. Wings. Length 7.7 mm; posterior half hyaline (most of cell r 5 and posterior to CuA 1), anterior half brown stained; very few microtrichia scattered on wing, veins brown, M 1 + 2 apically white, marginal wing cells closed except for cells r 4 and r 5 which are open; C terminating at junction with R 5; R 4 terminating in R 1; R 5 terminating in C; stump vein (R 3) absent at base of R 4; R 4 and R 5 (forming cell r 4) approaching each other at 2 / 3 of length, therefore constricting cell r 4; M 1 + 2 terminating in C; CuA 1 and CuA 2 split proximally to m-cu (cell m 3 narrow proximally); alula well-developed, but not touching scutellum medially; haltere light yellow.

Abdomen. Predominantly yellow, T 2 as wide as T 1, T and S apruinose, scattered white to yellow setae, longest on T 1; T 1 - 7 well-developed and visible; T 2 - 7 laterally brown; bullae on T 2 brown and transversely elongate. Terminalia not studied in detail.

Female. Scutum predominantly brown, setation much shorter; met femora less bulbous and expanded; proximal met tarsomere longer than 2 nd tarsomere, pulvilli on all tarsi about half the length of claws, only as wide as base of claws; wing length 8.4 mm; abdomen brown and yellow, T 1 brown medially and yellow laterally; T 2 proximally yellow, brown distally; T 3 - 8 and S 2 - 8 brown proximally and yellow distally, distal colouration less yellow on posterior T, only T 2 - 5 brown laterally. Genitalia. Ovipositor with acanthophorite plates each with 8 spurs; internal structures not studied.

Remarks: The holotype of this species is deposited in the Muséum national d’Histoire naturelle ( MNHN, Paris, France), but has not been studied. As mentioned above, the species identification is not entirely certain as there is no recent revision of this genus. In the key to species provided by Séguy (1941) it will run to Rhopalia olivieri , but Rhopalia oldroydi Lyneborg, 1970 , which was described from central Afghanistan, does match the species in many details as well. Having studied specimens indistinguishable from the ones above collected in Israel (manuscript in preparation), which is not too far from the type locality in Egypt, makes me believe that Rhopalia olivieri is also present in the Arabian Peninsula. Distribution: Egypt, UAE.