  We show in this paper that the set of irreducible components of the family of
Galois coverings of P^1_C with Galois group isomorphic to D_n is in bijection
with the set of possible numerical types. In this special case the numerical
type is the equivalence class (for automorphisms of D_n) of the function which
to each conjugacy class \mathcal{C} in D_n associates the number of branch
points whose local monodromy lies in the class \mathcal{C}.
