Key to females of Gastrosericus from the Arabian Peninsula

Unknown: female of Gastrosericus alwathbaensis

1 Marginal cell short, length of costal margin at most 1.2× as long as apical truncation of marginal cell (Figs 19, 69). UAE ................................................... Gastrosericus alwathbaensis Schmid-Egger, sp. nov. (presumed)

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

2 Pygidial plate uniformly covered with stout, conspicuous setae (Fig. 43)......................................... 3

- Pygidial plate all or partly asetose and shiny or with setae that are inconspicuous, or apically only with some distinct setae (Figs 22, 30)............................................................................................ 10

Pygidal plate with setae

3 Setae of gena near mandibular base at least 0.6× as long as width of mandibular base, erect or semierect (Fig. 81), (may appear appressed in specimen stored in ethanol). Propleuron near hindmargin with glabrous, triangular elevation that points posterad ................................................................................................... 4

- Setae of gena near mandibular base at most 0.6× as long as width of mandibular base, appressed (Fig. 77). Propleuron near hindmargin without elevation........................................................................... 6

4 Clypeal medial lobe straight, medially often with small tooth (Fig. 83). Abdomen in most specimens black (Fig. 81), abdominal base may also be red. Widespread in Arabia......................................... Gastrosericus waltlii Spinola

- Clypeus otherwise. Abdomen red........................................................................ 5

5 Clypeal lamella pointed, apex rectangular or nearly so, sometimes with small median point. Mid- and hindfemora black (Fig. 25). Smaller species, 7.5–9.0 mm. Jordan to Libya, not in Arabia..................... Gastrosericus drewseni Dahlbom

- Clypeal lamella with obtuse angle, nearly half rounded, medially with rounded point (Fig. 68). Legs all red (Fig. 66). Larger species, 9–11 mm. UAE .......................................... Gastrosericus sheikhae Schmid-Egger sp. nov.

6 Mesosoma red (Fig. 47). Propleuron laterally with sharp diagonal keel, its edge black. Clypeus medially with two transverse short and flat shiny carinae. 7.0 mm. UAE, Oman ..................... Gastrosericus pulawskii Schmid-Egger sp. nov.

- Mesosoma black. Propleuron without such keel. Clypeus flat.................................................. 7

7 ACM mesally without or only with very small emargination. Pronotum not or weakly impressed (compare Fig. 29). [Clypeus yellow. Small species, 7.0–8.0 mm]...................................................................... 8

- ACM medially emarginate. Pronotum with distinct narrow impression, “sulcate” (compare Fig. 56). [Clypeal medial lobe laterally with corner, clypeus black or red, only in G. sanctus yellow]............................................... 9

8 Clypeus arcuate, medially in some specimens with small emargination, laterally without corner (Fig. 42). Abdomen all red (Fig. 41). Widespread in Arabia … Gastrosericus moricei E. Saunders

- Clypeus straight, clypeal lobe laterally with corner. Abdomen black, apical depression dark reddish. Dhofar in southern Oman .................................................................................. Gastrosericus spec. A

9 Clypeus reddish to black. Hindtarsomere V as long as hindtarsomere II. Abdomen all red. Larger species, 9.5–10 mm. UAE .......................................................... Gastrosericus albidaaensis Schmid-Egger nov. spec.

- Clypeus yellow, in some specimens basally black (Fig. 62). Hindtarsomere V shorter than hindtarsomere II. Abdomen varying from all black to all red. Smaller species, 6.5–8.5 mm. Widespread in Arabia............. Gastrosericus sanctus Pulawski

Pygidal plate asetose, shiny

10 Pronotum laterally at most with inconspicuous impression, rounded (Fig. 29). [Body length 5.0– 7.5 mm. Abdomen and femora all red]. Widespread in Arabia..................................................... Gastrosericus electus Nurse

- Pronotum laterally with deeply impressed sulcus (=“sulcate”) (Fig. 56)......................................... 11

11 Hindtarsomere V with basoventral spines (Fig. 57)......................................................... 12

- Tarsomeres V without such spines...................................................................... 13

12 Gena simple. Apical margin of clypeal lobe sinuate, angulate laterally with lateral tooth in some specimens. Clypeus yellow. Body length 4.5–5.5 mm. Saudi Arabia, Oman ...................................... Gastrosericus vedda Pulawski

- Gena dentate below (Fig. 55). Apical margin of clypeal lobe divided into three arcuate portions, corner ill-defined (Fig. 54). Clypeus black. Body length 7.0–8.0 mm. UAE .................................. Gastrosericus sabulosus Pulawski

13 Clypeal disc without teeth [in G. turneri with V-shaped carina]................................................ 14

- Clypeal disc with two teeth (Figs 21, 39)................................................................. 15

14 Clypeus medially triangulary advanced, laterally with with V-shaped carina (Fig. 75). [Vertex with erect setae]. Larger species, 6.5–7.0 mm. UAE …........................................................... Gastrosericus turneri Arnold

- Clypeus medially with rectangular process, medially projecting into narrow process, as large as diameter of antennal base, process apically emarginate (Fig. 35). [Gena near mandible with prominent tooth (Fig. 36). Mesopleuron near tegula impressed, outer part swollen (Fig. 37).] Smaller species, 4.5–6.0 mm. Saudi Arabia, UAE ........ … Gastrosericus eremicus Pulawski

15 Abdomen black, at most terga I and II with some red. Pronotum laterally near foremargin between dorsal and lateral part without clear edge, more or less rounded. Gena (lateral view) below with minute, pointed tooth. Transition between underside of gena and lateral part of gena rounded. [Clypeus on disc with two small transverse lamellae. Lower margin of pronotum near propleuron with small, triangular tooth. Propleuron near hindmargin with small, triangular tooth, directed downwards]. Length 6.0 mm. Oman ...................................................................... Gastrosericus spec. B

- Abdomen red. Pronotum laterally near foremargin between dorsal and lateral part with distinct edge. Gena (lateral view) below with large tooth. Transition between underside of gena and lateral part of gena with edge, edge carrying a tooth......... 16

16 Underside of gena (near oral fossa) largely but flat impressed (Fig. 40). Teeth of clypeus lamelliform, medially often connected (is variable) (Fig. 39). Lower lateral margin of pronotum evenly rounded. Propleuron near hindmargin flat. Central Asia to Morocco, not recorded from Arabia......................................... Gastrosericus funereus Gussakovskij

- Underside of gena not impressed. Teeth of clypeus small, triangular (Fig. 21). Lower margin of pronotum enlarged, winged. Propleuron near hindmargin with large, triangular teeth on each side, directed backwards. UAE ............................................................................. Gastrosericus barqaalsuqoorensis Schmid-Egger sp. nov.