Key to species complexes and species of the Merodon bessarabicus subgroup (Distribution data are included) MALES 1 Tergites only with pale pile..............................................................................2 - Tergites with pale pile and stripes of black pile..............................................................7 2 Mesonotum only with pale pile...........................................................................3 - Mesonotum with both pale and black pile, black ones present at least near wing basis............................... 5 3 Tergite II (and III) with a pair of orange lateral spots............... Merodon luteomaculatus complex (South-East Europe) - Tergites uniformly dark brown to black (Fig. 9 a)............................................................ 4 4 Tergites II and III with a pair of lateral microtrichose stripes (Fig. 9 a); hind femur black except for paler apical margin (Fig. 9 b); pile on eyes black in upper 1/2....................................... Merodon legionensis (Iberian Peninsula) - Tergites usually without microtrichia (Fig. 7 a); hind femur with yellowish apical fifth, including triangular process (Fig. 7 c); pile on eyes black in upper 1/3.................................................... Merodon flavicornis (France) 5 Black pile on mesoscutum distributed only between wing bases (Fig. 15 a).............................................................................. Merodon ambiguus complex (Aegean islands, Balkan and Anatolian Peninsulas) - Pile on at least posterior half of mesoscutum black (as in Fig. 5 a)................................................ 6 6 Eyes in upper third with black pile; hind femora in apical half with black pile; almost all surface of mesoscutum covered with black pile, except pale stripes of pile on anterior margin; anterior half of scutellum with black pile, posterior half with pale pile (Fig. 4 b)........................................................... Merodon adriaticus sp. n. (Adriatic coast) - Eyes and hind femora mostly covered with pale pile; mesoscutum with black pile on posterior half; scutellum covered with pale pile (Fig. 12 b)......................................................... Merodon rufipes (Eastern Europe) 7 Mesoscutum covered with pale pile............... Merodon sapphous complex (Aegean islands and Anatolian Peninsula) - Mesoscutum with at least wing bases bearing black pile..................................................... .. 8 8 Eyes in upper half covered with black pile............. Merodon bessarabicus complex (Anatolian and Balkan Peninsulas) - Pile of eyes pale or with few black pile in apical fifth........................ Merodon quercetorum (Iberian Peninsula)

Published as part of Veselić, Sanja, Vujić, Ante & Radenković, Snežana, 2017, Three new Eastern-Mediterranean endemic species of the Merodon aureus group (Diptera: Syrphidae), pp. 401-434 in Zootaxa 4254 (4) on page 431, DOI: 10.11646/zootaxa.4254.4.1, http://zenodo.org/record/556010