A major component of Field Museum expeditions is examining the birds and mammals captured for parasites. Not only can parasites be important disease vectors, by sequencing their DNA we can gain insight not only into the evolution of the parasites themselves, but also into the evolution of their hosts. This is a hippoboscid fly. One way that lice--another parasite--move from one organism to another is by hitching a ride on a hipposcid fly.
Photo © Federico Pardo / The Field Museum