Suddenly you are aware of something strange on a nearby leaf, colors pulsating and changing in iridescent, metallic flashes like the flickering flames of copper sulfate. You are fortunate to be looking at a Great Purple Hairstreak, the possessor of the most wonderful color changes of any butterfly in America. One moment you see iridescent bluish-green, then royal purple, aquamarine blue, glints of violet and metallic green. This is because the butterfly is slowly moving its wings and each change in the angle of the sun hitting the prism-like cells of the wings creates a new symphony of wondrous color.
This is a tropical butterfly, fortunately, wandering northward as far as southern California, Illinois, and New Jersey, bringing the rich colors of the jungle into our more colorless norther lives. The farther north you live the rarer it becomes, but in Mexico and Central America, it is exceedingly common.
The name hairstreak comes from the hair-like tails possessed by most of the hairstreak butterflies and dangling from their rear wings. The function of these queer, hair-like tails is not fully understood.
The downy green caterpillar is decorated with darker green bands, obliquely striping the sides. It feeds on mistletoe and lives oak.