Does it sting? No
What does it eat? Asters
Will it seriously damage plants or trees? Not usually
Is it rare? No, but it isn't always common in all areas.
What does it turn into? The pretty Painted Lady butterfly
Can you raise it to an adult? Yes, if you give it an upright stick to pupate on.
The painted lady butterfly is likely the most wide-spread butterfly species in the world -- it occurs nearly everywhere, and has many subspecies and forms. The caterpillar is spiny but harmless, and in fact is the species most often included in butterfly rearing kits. In these kits, you receive a coupon to send in for eggs or newly hatched caterpillars, which feed on a kind of paste included in the kit. In nature, of course, the caterpillars feed on leaves, usually asters but also many other plants.
Painted lady butterflies are known to migrate in large numbers, spreading beyond their usual range.
The painted lady: Vanessa cardui