Key to the fossil Bibionidae from Radoboj

(females except for Penthetria cimicoides, Penthetria gracilis and Penthetria longa). Species described from other localities which have unconfirmed records from Radoboj are included.

1 Radial sector furcate, distally divided with veins R 2+3 and R 4+5. Crossvein R-M vertical. Legs slender................... 2

- Radial sector undivided. Crossvein R-M oblique. Legs more or less thickened ( Bibioninae)......................... 10

2 Vein R 2+3 long, more or less horizontal. (Genus Penthetria).................................................... 3

- Vein R 2+3 short, oblique to vertical. (Genus Plecia)........................................................... 7

3 Wing wider, length/width = 2.6–2.7....................................................................... 4

- Wing narrower, length/width ≈ 3.0........................................................................ 5

4 Wing apically broadly rounded, R 2+3 very long and horizontal.................................. Penthetria cimicoides

- Wing apically more pointed, R 2+3 shorter and more oblique...................................... Penthetria gracilis

5 Body and legs reddish brown...............................................................? Penthetria longa

- Body and legs coal-black............................................................................... 6

6 R 2+3 longer, straight, wing apically more rounded........................................... Penthetria anthracina

- R 2+3 shorter, distinctively curved, wing apically pointed...................................... Penthetria murchisonii

7 Very large species, body length ≈ 15 mm .......................................................... Plecia morio

- Smaller species, body length 12 mm or less................................................................. 8

8 R 2+3 basally distinctively curved. Femorae mainly pale............................................ Plecia bucklandi

- R 2+3 almost straight, legs entirely dark..................................................................... 9

9 Vein CuA 2 distally distinctively curved basad.................................................... Plecia lugubris

- Vein CuA 2 distally nearly straight............................................................ Plecia lygaeoides

10 Fore tibia cylindrical, with spines mesally. Thorax anteriorly with two transverse spine rows. Body ochreous-brown with dark head................................................................................... Dilophus pinguis

- Fore tibia spindle-shaped with apical spine. Thorax without spines. Body dark. (genus Bibio)........................ 11

11 Wing with radial area black, contrasting against the rest of wing. Very large species,> 15 mm ............ Bibio giganteus

- Radial area of wing not darkened. Often markedly smaller species............................................. 12

12 Wing with Radial sector less than twice as long as R-M.............................................. Bibio firmus

- Wing with Radial sector at least twice as long as crossvein R-M............................................... 13

13 Wing hyaline with dark veins and highly distinctive, dark pterostigma. Vein M 2 distinctively bent at junction with crossvein M-CuA................................................................................ Bibio crassinervis

- Wing veins apparently concolourous with membrane, pterostigma indistinctive. Vein M 2 straight at junction with crossvein M- CuA................................................................................... Bibio enterodelus