Cerambyx cinereus Fabricius, 1792 is preoccupied by Cerambyx cinereus DeGeer, 1775.
The name Diorthus simplex was validly used by Gahan (1906: 133); therefore, one of the conditions for the ICZN 23.9. (Reversal of precedence) can not be met. In fact, "the senior synonym or homonym has not been used as a valid name after 1899" (Art. 23.9.1.1.)