One hundred species of butterflies were observed during a two-year study conducted at Coronado National Memorial from 1996-1998. Another ten to fifteen species are thought likely to be here, but were not seen during the study. Compare this with the 180 species of butterflies recorded from the Huachuca mountains and surrounding area, or the 145 species reported just from Garden Canyon, a mid to high elevation canyon with permanent water.
One factor contributing to the high diversity of butterflies with the memorial is its location on the Mexican border, a region easily accessible to wandering and otherwise non-residential butterflies with origins to the south in Mexico. Also, its proximity to the San Pedro River, a natural corridor for northward straying butterfly species as well as a haven for native riparian lepidoptera, increases the odds of adding species to the park list.
Two factors limit butterfly diversity with the Memorial; absence of high elevation habitat and associated plants, and the absence of a good, permanent, water source. Butterfly density is usually higher on hilltops, in gullies, around high concentrations of good nectar flowers, and at isolated patches of standing water. While males of certain species use hilltops for mate location others may use gullies. The October blooms of desert broom, Baccharis sarathroides, provide excellent nectar sources and good butterfly watching opportunities.