The sole representative of its genus Dryas,[4] it is native from Brazil to southern Texas and Florida, and in summer can sometimes be found as far north as eastern Nebraska.

[6] Its caterpillar feeds on leaves of passion vines, including Passiflora affinis and yellow passionflower (P. lutea) in Texas.

Its mating behavior is complex and involves a prolonged courtship whose outcome appears to be controlled by the female.

Dryas iulia is common in the tropical and subtropical areas of North, Central, and South America.

In South America, throughout countries like Brazil, Ecuador, and Bolivia, the Julia butterfly is commonly distributed.

The butterfly is also widespread throughout a number of the Caribbean islands, with endemic subspecies located in Cuba, Dominica, the Bahamas, and Puerto Rico, among others.

The butterfly is also common in open areas such as gardens, cattle grazing lands, and forest clearings, due to human impact.

[10] D. iulia can be found on a few main hostplants (or shrubs in Latin America) including the passion vine of the family Passifloraceae.

Many members of the genus Passiflora have evolved to produce very tough, thick leaves that are hard to break down by caterpillars.

It involves male butterflies crowding around damp ground in order to drink dissolved minerals through a process of water filtration.

[15] Dryas iulia butterflies are part of the “orange” Müllerian mimicry complex, one of the similar Heliconian species that employ this protective tactic.

This has led to the development of cyanogenic glycosides that make the butterfly unpalatable to its predators, which come from a mixture of storage from their hostplant and larval synthesis.

[16]Dryas iulia eggs tend to be a light yellow color when laid, which turns to a darker orange or brown shade before hatching.

Each of the butterfly's eggs are separately laid onto new leaf tendrils of its host plant, usually the passionflower vine.

The caterpillars of the Julia butterfly have pink, gray, and black coloration throughout their body with maroon and cream patches.

For example, the only male behavioral acts found to be indicative of successful copulation occurred in response to signals of female receptiveness.

This raises the idea of an evolutionary basis for this behavior based on a conflict of interests between males and females of the species.

[7] The methods of mate selection (by which a female accepts or denies a male suitor) are not completely understood.

However, more research is needed to identify how different aspects of D. iulia’s physical features factor into mate selection.

This is likely from the yellow liquid that is produced from the tips of the long, black spines that cover its body, which is emitted as a predator deterrent related to their cyanogenic glycosides[8] D. iulia are commonly admired for their coloration.