The Arizona Sister, Adelpha eulalia, is a nymphalid butterfly native to North and Central America.  It occurs in the southwestern United States (far southeastern California, Arizona, New Mexico and Texas, sometimes ranging further north and east) through much of Mexico, south to Guatemala (Prudic et al. 2008).  The species is found in a wide variety of habitats where the caterpillar host plants (a variety of different species of oaks) are abundant (Ferris & Brown 1981, Harry 1994, Prudic et al. 2008).  In much of its range, there are two broods a year, with adult butterflies flying from March–early May and August–early November in southern populations, April–June and August–December in northern populations (Prudic et al. 2008).

The Arizona Sister was long considered a subspecies of Adelpha bredowii Geyer, 1837 (Carpenter & Hobby 1944, Willmott 2003, Stout 2005). Based on genetic, morphological, and geographic evidence, Prudic et al. (2008) recommend that Adelpha eulalia, Adelpha californica and Adelpha bredowii are treated as separate species.