Giant water bugs, and their nymphs, are fierce predators feeding on small fish, tadpoles, salamanders, even small frogs. They usually hunt by lying-in-ambush clutching a submerged plant or rock with only their breathing tube sticking above the surface. Any passing motion can trigger a rapid "lunge and grab" with the hook-tipped front legs. (My captive bug would even lunge and grab the net or anything else I stuck into the aquarium. I had been warned not to stick my fingers in front of its face and I willingly complied. ) If prey is successfully grasped it is quickly dispatched with a pierce from the bug's needle-like rostrum (fused mouth parts) and an injection of toxic enzymes. These enzymes poison the prey and begin to digest it at the same time. Once the enzymes have completed their job the bug again uses its rostrum, but this time sucks out the pre-digested soup that was its prey, leaving a limp bag of skin. If this critter sounds like some kind of mini-monster, don't despair. In the orient, giant water bugs are renowned as a great delicacy, so, as always, critters seem to have more to fear from us than we from them.
The bug's hunting technique is not limited to lying in wait. It will actively swim after prey that is a ways off or that it has missed on its first lunge. The hind legs are paddle-shaped and equipped with long hairs that fan out as the leg is stroked to increase its effective surface area. Giant water bugs can swim, or scull, through the water rapidly in search of prey or to evade becoming prey themselves.
Giant water bugs, ya gotta love'em! So, keep your eyes peeled in parking lots near water, but if you find a live one, pick it up carefully!