The concept of an "aggressive" butterfly always cracked me up. What are they going to do, flap you to death?
Though once, I found a tiny, inch-long parsleyworm on my porch, and when I went to pick it up to return it to the garden, it did that head-lashing orange-tentacle thing and made me reflexively jump. Silly caterpillar.
YAY! These, as caterpillars, appeared in droves at my childhood home every year to put chrysalises EVERYWHERE and then pop out around the first week of May. We loved to watch them emerge and dry their wings, then fly away. It was so exciting. Just don't step accidentally on the caterpillars- theyre black, orange speckled and spiny, and the sting hurts like bejeebers.
Actually, that's an urban legend--butterflies are just fine if handled delicately. Heck, they can survive bird attacks that take off half their wing! People even band butterflies like birds. You don't want to paw at them, obviously, but they'll be just fine if their wings are touched.