  We generalize a result for the translation $C_0$-semigroup on $L^p(\R_+,\mu)$
about the equivalence of being chaotic and satisfying the Frequent
Hypercyclicity criterion due to Mangino and Peris to certain weighted
composition $C_0$-semigroups. Such $C_0$-semigroups appear in a natural way
when dealing with initial value problems for linear first order partial
differential operators. We apply our result to the linear von Foerster-Lasota
equation arising in mathematical biology. Weighted composition $C_0$-semigroups
on Sobolev spaces are also considered.
