Key to males of Gastrosericus from the Arabian Peninsula

1 Marginal cell short, length of costal margin at most 1.2× as long as apical truncation of marginal cell (Fig. 19). [Clypeus yellow. Sterna II–V deeply impressed on whole width (Fig. 17). AS 3 slighly shorter than wide, AS 4 and following 1.3–1.4× as long as wide (Fig. 16)]. Body length 4.1 mm. UAE ....................... Gastrosericus alwathbaensis Schmid-Egger sp. nov.

- Marginal cell longer, length of costal margin at least 1.5× as long as apical truncation of marginal cell (Fig. 85).......... 2

2 Gena below with long semierect or erect setae, at least as long as 0.6× basal mandibular diameter (may appear appressed in specimens stored in ethanol) (Fig. 84). Sterna III and IV with deep impression, covered with long yellow setae, surrounded by sharp edge (Figs 73, 86)............................................................................... 3

- Gena with shorter and appressed setae. Sterna without impression, if with setae, then they origin on flat surface of sterna (Fig. 45)................................................................................................ 5

3 Tibiae and tarsi all yellowish-red. Abdominal segment VII red [Abdomen in most specimens all red] (Fig. 26). Jordan to Libya, not in Arabia …............................................................ Gastrosericus drewseni Dahlbom

- Tibia black, or partly dark red. Abdominal segment VII black.................................................. 4

4 Abdomen in most specimens all black, apical tergal depression with some red. Legs black (Fig. 81). Wing venation predominantly dark. [Erect pilosity denser and longer in direct comparison with following species]. Widespread in Arabia..................................................................................... Gastrosericus waltlii Spinola

- Abdominal segments I–III or I–VI red. Tarsi completely and hindfemur partly red (Fig. 70). Wing venation of forewing in basal half yellow, apart from costal vein. UAE ............................. Gastrosericus sheikhae Schmid-Egger sp. nov.

5 Sterna III–IV with well definined patch of long white or yellow setae (Figs 45, 51, 65).............................. 6

- Sterna III–IV without setae, similar to remaining sterna...................................................... 10

Sterna with setae

6 Clypeal lobe slightly rounded or straight between lateral corners (Fig. 64). [Clypeus all yellow, lobe wide, distance between lobe comers 2.0 x distance between corner and orbit, clypeal lobal corners more prominent. Inner mandibular margin without tooth. Sternal setae nearly appressed]. 5.5–6.0 mm. Widespread in Arabia............... Gastrosericus sanctus Pulawski

- Clypeal lobe triangular................................................................................ 7

7 Clypeal lobe with obtuse angle.......................................................................... 8

- Clypeal lobe triangular, rectangular or with acute angle....................................................... 9

8 Clypeus yellow. Sternum VII rounded (Fig. 46). Femora apically, tibiae, tarsi and pronotal lobe above whitish, remaining legs red (Fig. 44). Smaller species, body length 5.0–6.0 mm. [Flagellomeres dark, contrasting with yellow scape. Setae of sterna III and IV directed backwards. Apical tergal impressions reddish-whitish, slightly paler than remaing parts of red terga]. Northern half of Africa, Arabia to India ................................................ Gastrosericus moricei E. Saunders

- Clypeus black. Sternum VII emarginate (Fig. 52). Legs and pronotal lobe red. Larger species, body length 8.1 mm. United Arab Emirates, Oman ....................................................... Gastrosericus pulawskii Schmid-Egger

9 Clypeus black, abdomen red (Figs 11, 12). Body length 8.2 mm. UAE .. Gastrosericus albidaaensis Schmid-Egger, sp. nov.

- Clypeus yellow, abdomen black. Body length 6.5 mm. Dhofar in southern Oman ................. Gastrosericus spec. A

10 Clypeal lobe pointed mesally (or at most rectangular), not angulate laterally, its apical margin forming single curved line with sides of clypeus..................................................................................... 11

- Clypeal lobe angulate laterally, or, if not, with rounded arcute apical margin, medially never pointed.................. 13

11 Mesonotum next to tegula with longitudinal impression, outer part near tegula swollen. [Abdomen red]. Saudi Arabia, UAE .......................................................................... Gastrosericus eremicus Pulawski

- Mesonotum not impressed............................................................................. 12

12 Apical clypeal margin rectangular (Fig. 59). Setae of vertex appressed. AS 3 somewhat shorter than AS 4 (Fig. 60). UAE ............................................................................ Gastrosericus sabulosus Pulawski

- Apical clypeal margin acutely pointed (Fig. 78). Setae of vertex erect, as long as fore ocellar diameter (difficult to see in worn specimens) (Fig. 78). AS 3 as long as AS 4. UAE ..................................... Gastrosericus turneri Arnold

13 Clypeus yellow..................................................................................... 14

- Clypeus black. [Apical clypeal margin with obtuse angle].................................................... 15

14 C lypeal lobe advanced, widely rounded, without tooth (Fig. 32). Abdomen red (Fig. 31). Antenna including scape all yellow. Widespread in Arabia............................................................ Gastrosericus electus Nurse

- Clypeal lobe slightly rounded, on each side with distinct tooth. Abdomen in most specimens all black. Scapal venter yellow, flagellum brownish or black with some yellow. Saudi Arabia, Oman .................... Gastrosericus vedda Pulawski

15 Clypeal lobe rectangular (Fig. 24). [midleg all black, remaining legs broken off in type male] UAE .......................................................................... Gastrosericus barqaalsuqoorensis Schmid-Egger sp. nov. - Clypeal lobe obtuse.................................................................................. 16 16 Legs black apart from white band on hindtibia above. Oman …................................. Gastrosericus spec. B - Legs in greater part yellow: at least band on midtibia below, hindtibia above, and all tarsi. Central Asia to Morocco, not recorded from Arabia ….................................................... Gastrosericus funereus Gussakovskij