  Among the newly observed structures in the heavy quarkonium mass region, some
are proposed to be hadronic molecules. We investigate the consequences of heavy
quark flavor symmetry on these heavy meson hadronic molecules. The symmetry
allows us to predict new hadronic molecules on one hand, and test the hadronic
molecular assumption of the observed structures on the other hand. We explore
the consequences of the flavor symmetry assuming the X(3872) and $Z_b(10610)$
as a isoscalar $D\bar D^*$ and isovector $B\bar B^*$ hadronic molecule,
respectively. A series of hadronic molecules composed of heavy mesons are
predicted. In particular, there is an isoscalar $1^{++}$ $B\bar B^*$ bound
state with a mass of 10580 MeV which may be searched for in the
$\Upsilon(1S,2S)\pi^+\pi^-\pi^0$ mass distribution; the isovector charmonium
partners of the $Z_b(10610)$ and the $Z_b(10650)$ are also predicted, one of
which probably corresponds to the very recently observed $Z_c(3900)$ and
$Z_c(4025)$ resonances by the BESIII Collaboration.
