  We study the asymptotics conjecture of Malle for dihedral groups $D_\ell$ of
order $2\ell$, where $\ell$ is an odd prime. We prove the expected lower bound
for those groups. For the upper bounds we show that there is a connection to
class groups of quadratic number fields. The asymptotic behavior of those class
groups is predicted by the Cohen--Lenstra heuristics. Under the assumption of
this heuristic we are able to prove the expected upper bounds.
