The Gulf Fritillary or Passion butterfly (Agraulis vanillae) is a striking, bright orange butterfly of the family Nymphalidae, subfamily Heliconiinae. These were formerly classified in a separate family, the Heliconiidae or longwing butterflies, and like other longwings this species does have long, rather narrow wings in comparison with other butterflies. It is not closely related to the true fritillaries. It is a medium to large butterfly, with a wingspan of from 6—9.5 cm. Its underwings are buff, with large silvery spots. It takes its name from the fact that migrating flights of the butterflies are sometimes seen over the Gulf of Mexico.

The Gulf Fritillary is commonly seen in parks and gardens, as well as in open country. Its range extends from Argentina through Central America, Mexico, and the West Indies to the southern United States, as far north as the San Francisco Bay Area on the west coast. It is occasionally found further north in the US.

From Wikipedia entry for Gulf Fritillary.

Special thanks to Shannon Smith!