Green caterpillars on beans

The Wife (TM) has been finding green caterpillars munching on the leaves of her beans. Can anyone identify what this caterpillar was, just before She whacked it? It was about 1/2 inch long. Is there a Weapon of Mass Destruction that will kill any that are still lurking? We are in Eastern Ontario. Here is a URL where you may see the beast:
http://web.ripnet.com/~jcarter/worm.html -- Gardening Zones Canada Zone 5a United States Zone 3a Near Ottawa, Ontario
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Larval forms of insects. "worms" ;caterpillars"etc can be controlled by applying a spray of BT--a biological pesticide derivered from a bacterium.
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It look to me like the larvae of the black swallowtail butterfly: http://www.npwrc.usgs.gov/resource/distr/lepid/bflyusa/pa/895.htm
although they are usually found on dill and parsley. I am always pleased to spot these, and gladly sacrifice a bit of vegetation to help propagate the species. They are seldom present in large numbers, and do little damage in the overall scheme of things. Butterfly numbers in general are declining due to indiscriminate pesticide use, so I try to do my part in creating mini-ecosystems for the adults and the larvae.
Actually, I'm jealous...I haven't seen any of these guys yet this year, probably due to last year's drought and this year's cold wet spring, and I miss them. The only visitors I have to my butterfly bushes are the ubiquitous cabbage whites.
Cheers, Sue

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that
a URL

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Hey, that worm has relatives in my garden eating my tender cabbage plants. I garden to the West of Ottawa near the village of Barry's Bay. It looks like the larval stage of the white cabbage moth. What a rotten pest. I use BT powder. Ritchie Feed and Seed has BT. Good luck
Farmer John

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