I have a photo of the immature nymph of this insect at http://www.pbase.com/jmhoying/image/99504193 .
The wheel bug adult usually measures from 1 to 1.25 inches long. This assassin bug is a dark robust, grotesque creature having long legs and antennae, stout beak, large eyes on a slim head, and a prominent thoracic, semicircular crest suggesting a cogwheel or chicken's comb. This is the only insect species in the United States with such a crest. The number of teeth (tubercles) in the crest varies from eight to 12. Females are longer and wider than males, with the abdominal margins being more widely exposed in the females. A very fine yellowish pubescence is present over most of the body, except the elytral membrane which produces bronze-colored reflections. The overall color is mostly dark brown. Variable amounts of tiny white patches or granules are scattered throughout the pubescence.