If you're one of the many people who refer to insects as "bugs," you're right on when it comes to this huge beast. It is, figuratively and biologically, a true "bug." On top of that, it's the largest insect in North America. To address it scientifically, it's: Family, Belostomatidae - Order, Hemiptera - Genus, Lethocerus - Species, americanus
Although more commonly known as the "toe-biter." Or in Florida, more colorfully, "alligator ticks."
Over the years people have been swimming in ponds, lakes and slow-moving streams, a few have discovered the awful pain of a giant water bug shoving its proboscis into their toe. Several victims have been curious about the gigantic bug, and some even went on to study them. If you Google, "giant water bug" you will connect to a link that I think is in error, Kathleen Pohl's book, Giant Water Bugs, which is (supposedly) for sale for $100,000, but the real price is $17.87. Another link says that in Thailand they're a delicacy; you can buy them by the pound, then fricassee and eat 'em like Buffalo wings.
These huge bugs are entirely aquatic and catch their prey by ambushing them, usually hanging head-down from aquatic vegetation patiently waiting for an unsuspecting small fish, pollywog or other aquatic organism to go swimming by. With a burst of speed from their powerful paddle-like legs, they slam into their prey, grasp it by the hooked front legs and push their sharp sucking mouth-part into the quarry. There is nothing "nice" about a waterbug feeding on its prey.
The first thing that happens when that sharp proboscis penetrates the outside skeleton of an insect (chiton), flesh of tadpole - or the skin of your toe - is the injection of powerful enzymes. These chemicals are designed to break down flesh into a delicious soup so it can be sucked into the bug's stomach. (I told you, there's nothing nice about the way waterbugs eat.)
If the mouth is in a human, the enzymes still go to work digesting flesh. The longer this goes on the worse it will hurt, and the chance for permanent damage accelerates. So, if you pick one up, get rid of it quickly.
In late summer water bugs take to the air, looking for two things: 1) a suitable place to spend winter, and/or 2) new territory to set up housekeeping. In the first instance, the wintering habitat must be a deeper body of water that will not freeze solid. Like all creatures that must survive winter, the giant water bug - all fattened up with the prey they sucked dry in summer - will literally hang out beneath the surface on submerged vegetation, slow their metabolism down to the torpid state where they can keep their body just barely alive, and live off their fat.
As with many insects, giant water bugs are also attracted to lights at night, which is often their undoing. Sometimes they mistake the shiny body of a motor vehicle for the surface of a pond reflected in the lights, and dive straight into it. The result of this brash behavior is usually the death of the mistaken insect.
Way back in Ancient Times when I tooled around in a snazzy 1949 black Chevy convertible, I was parked in a station at night filling it up with 21-cents-a-gallon premium gasoline, when, suddenly, "clang!" something bounced off the hood. I thought it was a rock someone had tossed at me, but when I found the object it was a smashed giant water bug that had mistaken the big hood of the Chevy for a small pond.
In closing, if you come upon a giant water bug some evening lying dead under the lights, with what looks like its guts coming out the back end, don't be fooled. If you pick it up you may find (painfully) that is was "playing dead."