You may someday wander down a road in the American Tropics and see Julia butterflies clustered along the way in hundreds and thousands, sipping at the damp places, or rising in glittering orange clouds into the air. If you try to catch one, however, it suddenly turns into a demon of action, storming away through the air like a frightened hummingbird. Watch a Julia flitting along the edges of the woods and sometime you may see the butterfly it mimics, a similar-looking Heliconian. The Heliconian is poisonous, but the Julia is not. However, birds leave the Julia along because they think it too is poisonous. The peculiar thing is that usually, the non-poisonous Julia is much more common than the poisonous butterfly it mimics.
Another difference between the Julia and one it mimics is that the Julia has a much stronger flight and widely roams over miles of the country while the other butterfly is usually found only along the edges of woods and is a poor flier. It almost seems as though the Julia has become such a swift flier that it no longer needs the protection of looking like something poisonous to eat.
The caterpillars have long, branching spines and live on leaves of the Passion Flowers, which are common along many a tropical American road.