  For an arbitrary commutative ring k and t in k, we construct a 2-functor S_t
which sends a tensor category to a new tensor category. By applying it to the
representation category of a bialgebra we obtain a family of categories which
interpolates the representation categories of the wreath products of the
bialgebra. This generalizes the construction of Deligne's category Rep(S_t,k)
for representation categories of symmetric groups.
