The black saddlebags is named for the blackish saddle-shaped markings at the base of the hindwing; unfortunately these don't show up very well in some of these pictures.   This page shows the 'saddle' in closeup.   This species alternates between fairly long, cruising flight (especially in the morning) with perching, often on tall, isolated twigs.   It has a common close relative with similar habits, the red saddlebags.   One of the photos below shows a mating pair; another shows a male (left) and female flying in tandem during mating and oviposition.   I took the pictures with a long telephoto lens at the San Jacinto Wildlife Area near Riverside, California.