Identification key to males and females of Nyssonini from Arabian Peninsula

The females of Brachystegus nemkovi, B. schneideri, Synnevrus arabicus and the males of Nysson waleedi and N. woodi are unknwon.

1. Hindtibia irregulary serrate on dorsal surface. Median vein of hindwing starts behind submedial cell (Fig. 1) Male S 2–5 medially with row of long white bristles (Fig. 7)......................................... 3 ( Brachystegus A. Costa)

– Hindtiba with simple spines only. Median vein of hindwing starts inside submedial cell (Fig. 2). Male sterna simple...... 2

2. Mesoscutum with fine punctation, interspaces at least as large as puncture diameter (figs 15, 18). Apical margin of T 1–3 simple. [Clypeus without transverse carina]................................................. 5 ( Nysson Latreille)

– Mesoscutum with deep, comb-like punctation, punctures larger than interspaces, interspaces dull or finely micropunctured (Fig. 8). Apical margin of T 1–3 with obliquely protruding lamella above tergite edge, creating double edge .....................................................................................................6 ( Synnevrus A. Costa)

3. Clypeus evenly rounded, yellow (Fig. 5). Band of T2 continuous (Fig. 3). Median tooth of male T7 pointed, T6 yellow (Fig. 6). 10.2 mm. Saudi Arabia. (Female unknown).............. Brachystegus nemkovi Schmid-Egger & Al Jahdhami sp. nov.

– Clypeus with transverse conspicous edge along its whole width, roof like seen in profile, black (Fig. 10). Band of T2 interrupted (Fig. 8, 11). Male: Median tooth of T7 rounded or truncate, T6 black or reddish (fig. 14)............................. 4

4. Pronotum with yellow lateral spots, scutellum black (Figs 8, 11). Antenna black, with apex red in male. T 1–4 with lateral yellow spots, in male also T5, black space between spots at least as large as yellow spots (Figs 8, 11). 8.0– 8.5 mm. Northern Oman .................................... Brachystegus samadashanensis Al-Jahdhami & Schmid-Egger sp. nov.

– Pronotum and parts of scutellum red (Fig. 12). Antenna red (Fig. 13). Only T1 with lateral yellow spots, T 2–6 with yellow band, medially shortly interrupted in T2-3 (or T2-T4), continuous at least in T6 (Fig. 14). 8.5–10.0 mm. (Female unknown). Northern Oman ................................. Brachystegus schneideri Schmid-Egger & Al Jahdhami sp. nov.

5. Mesoscutum shiny, with scattered fine punctation. Head and mesosoma red (Fig. 15). T 1–3 with thin continuous yellow bands. Northern Oman. 3.5 mm. (Male unknown).................... Nysson waleedi Al-Jahdhami & Schmid-Egger sp. nov.

– Mesoscutum dull, with denser and larger punctation, punctures approximately a diameter apart. Head and mesosoma black, pronotum and scutellum with yellow spots and some red, propodeum laterally red. T 1–5 with large lateral spots or continuous bands (Fig. 18). 4.5 mm. (Male unknown). Northern Oman, Saudi Arabia ................................................................................................ Nysson woodi Al-Jahdhami & Schmid-Egger sp. nov.

6. Clypeus with sharp transverse lamella, indistinct in male, ACM with two medial teeth (Fig. 28). Pronotum laterally rounded or with obtuse angle. [Pronotum red, remaining mesosoma black. Only T 1–2 with yellow band or spots.] 6.0- 6.5 mm. Saudi Arabia .......................................... Synnevrus mekkahensis Schmid-Egger & Al Jahdhami sp. nov.

– Clypeus flat or with rounded transverse step. ACM different. Pronotum laterally rectangular or pointed................. 7

7. Mesosoma all or largely red (Figs 22, 24). Clypeus forming rounded step just before apex. ACM without teeth. 4.5–6.0 mm. Oman, Saudi Arabia, UAE ................................................. ... Synnevrus barrei Radoszkowski

– Mesosoma all or largely black, or with withish spot or band (Figs 21, 25, 31, 32). Clypeus flat, ACM with teeth.......... 8

8. Pronotum black with some red only (Fig. 21). Scutellum black, basally red. T 1–6 with lemon yellow bands or spots. Larger, 6.0 mm. Male T7 with medial tooth larger and as long as lateral teeth, apex without long pilosity. (Female unknown). Saudi Arabia ................................................................ Synnevrus arabicus Gadallah & Edmardash

– Pronotal collar whitish (Fig. 31, 32). Scutellum basally with white spot. Only T 1–3 with whitish yellow spots or bands. Smaller, most specimens between 4.5–6.0 mm. Oman, Saudi Arabia, UAE ............... Synnevrus ohli Schmid-Egger