Tachycixius
Wagner, 1939
| 1 | Aedeagus with one movable subapical spine on the left and one on the right side of the theca. | 3 |
| Arrangement and/or number of movable subapical spines different. | 2 | |
| 2 | Aedeagus with two movable subapical spines at the right side of the theca; sometimes an additional spine is present on the left side. | T. canariensis, T. lavatubus, T. crypticus, T. retrusus |
| Aedeagus with three long falcate appendages arising from the middle and with a small bifid basal ventral tooth. | T. perarmata | |
| 3 | Movable spines curved, bifurcate (at least one of them). | T. viperinus, T. bidentifer, T. bifurcatus, T. chevsureticus, T. creticus, T. cypricus |
| Movable spines acute with a single tip. | 4 | |
| 4 | Theca with a thorny crest on ventral side. | T. venustulus |
| Theca without a thorny crest on ventral side, but sometimes rigid spines or a crest are present. | 5 | |
| 5 | Theca with a rigid bifurcate process on ventral side. | T. logvinenkovae |
| Ventral part of theca different. | 6 | |
| 6 | Postclypeus distinctly swollen. | T. pyrenaicus, T. distinctus, T. gravesteini |
| Postclypeus normal, not swollen. | 7 | |
| 7 | Medial part of theca ventral with three rigid, spine-like processes. | T. desertorum, T. tigrinus |
| Medial part of theca ventral with one rigid, spine-like process. Sometimes additional spines at the base of the theca. | T. pilosus, T. longiceps, T. ligustinus, T. remanei, T. soosi, T. arzonei |
