James
This is a photo of a wheel bug nymph or young stage of a large bug known as the Wheel bug. The nymphs and adults are great predators to have in the garden to get rid of caterpillars, aphids, etc.
They overwinter in the egg stage then emerge in spring to grow into the adults. There is just one generation per year.
CAUTION: The adult wheelbug is reported to inflict a very painful bite. It has been reported use of ammonia water or Epsom salts is helpful in relieving pain from the bite.
Here is a site for more information:
http://bugguide.net/node/view/454
