  Combinatorial Hopf algebras arise in a variety of applications. Recently,
Aguiar and Mahajan showed how many well-studied Hopf algebras are closely
related to Hopf monoids in species.
  In this paper, we study Hopf monoids in graphical species, giving a
`graph-theoretic' analogue to the work of Aguiar and Mahajan. In particular,
several examples of Hopf monoids in graphical species are detailed, most of
which are related to graph coloring, or hyperplane arrangements associated to
graphs.
