Answer: Without seeing the insect I'm only venturing a guess, but they could be Red Milkweed Beetles, especially if the head is red, as well. You might try looking in an insect book to see if you can find the beetle. The Audubon Society's Field Guide to North American Insects has terrific pictures! (ISBN# 0-394-50763-0.
They probably won't need control, but we won't know for sure without positive identification. Check your local library or bookstore for the Audubon book before you decide the plants need to be treated.
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