  We show that if a universal theory is not monadically NIP, then this is
witnessed by a canonical configuration defined by an existential formula. As a
consequence, we show that a hereditary class of relational structures is NIP
(resp. stable) if and only if it is monadically NIP (resp. monadically stable).
As another consequence, we show that if such a class is not monadically NIP,
then it has superexponential growth rate.
