Key to males of Thaumastocephalus

1 Small species, body length under 1.85 mm, aedeagus (Fig. 1)............................... T. bilandzijae Poggi et al.

- Larger species, body length more 1.90 mm ................................................................. 2

2 Protibiae in males modified, with well-defined median tooth................................................... 3

- Protibiae in males slightly modified, median tooth minuscule or absent........................................... 4

3 Large species, body length 2.2 mm, head much longer than wide, ratio: 1.43–1.47, aedeagus (see Poggi et al. 2001: Fig. 10)................................................................................ T. folliculipalpis Poggi et al.

- Small species, body length about 1.95 mm, head shorter than wide, ratio: 1.30, aedeagus (Fig. 7).......... T. dahnae sp. n.

4 Larger species, body length over 2.5 mm, aedeagus (Fig. 6)........................................ T. troglavi sp. n.

- Smalle species, body length under 2.0 mm................................................................. 5

5 Antennae short, less than 0.85 mm long, scape more than 2.3 times as long as pedicel, terminal antennomere short, less than 4.00 times as long as antennomere X...................................................................... 6

- Antennae long, about 0.88 mm long, scape less than 2.2 times as long as pedicel, terminal antennomere long, 4.25 times as long as antennomere X, rostrum long, only 1.78 times as wide as long, aedeagus (Fig. 5)................. T. slavkoi sp. n.

6 Elytra short, less than 1.2 times as long as pronotum, aedeagus (Fig. 4)............................ T. rujnicensis sp. n.

- Elytra long, more than 1.3 times as long as pronotum......................................................... 7

7 Rostrum long, about 2.3 times as wide as long, aedeagus (Fig. 3)................................... T. marsici sp. n.

- Rostrum short and wide, about 3.0 times as wide as long, aedeagus (Fig. 2).............................. T. kirini sp. n.