This is a Giant Water Bug. The body is 7 cm long.
Also called a Toe-Biter, apparently has one of the worst insect bites in North America.
The speciman above was obtained in Corvalis, Oregon. I found it dead and let it dry, pinned to a board. I then found a glass ash try at a Goodwill and encased the bug in two layers of Easy Cast epoxy. I’ve had trouble with epoxy in the past, including bubbles, poor mixing/amounts (causing it to never harden), and embedded items floating to the surface. Luckily, it turned out pretty well this time!
The Giant Water Bug is in the order Hemiptera, shared with cicadas, leaf hoppers, and aphids. A defining feature in this order is a beak that is used to pierce plants to suck sap, or in this case, defend against curious human hands and pierce prey.
Giant Water Bugs are aquatic predators that live in slow flowing water like ponds and lakes. They lie in wait for their unsuspecting prey which can range from other aquatic insects, to fish and frogs. When they strike, they grip their prey firmly with their front legs like a praying mantis and use their beak to inject a digestive enzyme and suck up the liquidy remains (*slurp!*). Here’s some youtube footage of a Giant Water Bug making a meal out of a goldfish.
A few years ago, I had two smaller (~3 cm long) water bugs as pets in an aquarium, like the one below (a different genus than the large bug above). They were neat, but I found I had to practically force feed them crickets held with tweezers (like this video). Also, to the distress of my roommate and guests, one mysteriously disappeared through the screen roof of the aquarium…