My neighbor, who’s an exterminator, never saw anything like this guy. He looks like a cross between a stegosaurus and a stick bug. In searching the Internet I just found out that he is a wheel bug, the largest of the assassin bugs. They also said that they could grow to be 1 ½ inches long. If that’s true then this one was a world record; I’d say he was approx. 5 – 6” long, not counting the antennae. This image is actually rotated as he was crawling up the wall towards the windowsill. He then flew off.
The adult wheel bug 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.
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.