  We show that, if E is a Landweber exact ring spectrum, then the category of
E_*E-comodules is equivalent to the localization of the category of
BP_*BP-comodules with respect to the hereditary torsion theory of v_n-torsion
comodules, where n is the height of E. In particular, the category of
E(n)_*E(n)-comodules is equivalent to the category of
(v_n^{-1}BP)_*(v_n^{-1}BP)-comodules. We also prove structure theorems for
E_*E-comodules; we show every E_*E-comodule has a primitive, we classify the
invariant radical ideals, and we prove a version of the Landweber filtration
theorem.
