Syrphidae

Dawah, Hassan A., Abdullah, Mohammed A., Ahmad, Syed Kamran, Al-Dhafer, Hathal & Turner, James, 2020, An overview of the Syrphidae (Diptera) of Saudi Arabia, Zootaxa 4855 (1), pp. 1-69 : 11-12

Key to the genera of Syrphidae from Saudi Arabia

1 Humerus (postpronotal callus) bare...................................................................... 11

- Humerus partly or completely covered with setulae......................................................... 11

2 Face entirely black.................................................................................... 3

- Face partially or entirely yellow.......................................................................... 4

3 Abdomen very elongated, waisted and slender................................................ Allobaccha Curran

- Abdomen not strikingly waisted, slender only in the male..................................... Melanostoma Schiner

4 Tergite 1 well developed, especially on disc where it is frequently half as long as tergite 2, -always extending well beyond scutellum; sublaterally about three quartes as long as tergite 2; tergites punctate.................................... 5

- Tergite 1 fused to tergite 2, often further tergite fused, eye haired, either on lower part or in vertical lines... Paragus Latreille

5 Pleura with distinct yellow markings. Mesonotum dark in ground colour and witha yellow lateral line.................. 6

- Pleura of a dark ground colour throughout.................................................................. 9

6 Antenna elongate, as long as the head. Abdomen robust, wider than the thorax. Wasp-mimics......... Chrysotoxum Meigen

- Antenna short. Abdomen narrower, especially in males....................................................... 7

7 Membrane of anal lobe of wing and alula covered with microtrichia. Male hind trochanter lacking any projection......... 8

- Wing membrane lacking microtrichia basad of mouth of subcosta in costa though there may be a few scarcely discernible microtrichia on alula. Male hind trochanter ventrally with a downwardly-directed spike that is as long as tibial width................................................................................................. Ischiodon Sack

8 More robust flies. Abdomen in both sexes as wide as or wider than the thorax. male genital capsule small................................................................................................ Allograpta Osten Sacken

- Slender flies. Male abdomen slightly to distinctly waisted and with genital capsule large Sphaerophoria Le Peletier & Serville

9 Eye densely long-haired............................................................................... 10

- Eye bare.......................................................................... Eupeodes Osten Sacken

10 Frons in both sexes seen in profile not to be swollen and projecting above eye. Tergites essentially yellow with an apical black transverse band and with 1 and the base of 2 also black the yellow parts conspicuously pale haird. Postpedicel cone-shaped, twice as long asdeep................................................................. Betasyrphus Matsumura

- Frons in both sexes seen in profile to be swollen and projecting above eye. Tergites dark in grossed colour, 2–4 bearing a pair of curved yellow markings that may be fused medially. Wing membrane largely devoid of microtrichi...... Scaeva Fabricius

11 Apical crossvein of vein M1+2 at mid length recurved towards base of wing......................... Eumerus Meigen

- Apical crossvein not recurved.......................................................................... 12

12 Face deeply concave, the mouth margin medially projecting forward of vibrissal angle. Dorsum of abdomen flat.............................................................................................. Orthonevra Macquart

- Not this combination of characters....................................................................... 13

13 Section of vein R4+5 between inner crossvein and wing apex deeply looped towards hind margin of wing.............. 14

- No such loop present, the vein only slightly curved......................................................... 15

14 Eye either with numerous dark spots distributed over its surface or with five dark vertical lines......... Eristalinus Rondani

- Eye devoid of such markings....................................................... Phytomia Guérin Méneville

15 Postpedicel with a distinct dorsally-situated arista. Hind femur swollen. Small narrow-bodied species................................................................................................ Syritta Le Peletier & Serville

- Postpedicel with a short apically-situated robust arista. Hind femur swollen. A long antennifer present. Postmetacoxal bridge incomplete......................................................................................... 16

16 Abdomen petiolate, second segment at its narrowest part much narrower than first and third segments.................................................................................................... Monoceromyia Shannon

- Abdomen not petiolate, second segment as broad as or broader than the first....................... Ceriana Rafinesque