These giant water bugs are carnivorous, preying on basically anything it can grab onto.  The most common prey for these bugs are snails, tadpoles, insects and other aquatic invertebrates, and even some small frogs and fish.  Belostoma flumineum hunt their prey using an ambush approach. ( 2012)  They lie motionless in the water, (resembling dead leaves, so as not to be an easy target for predators) waiting for unsuspecting prey to come by.  When an easy target shows up, it jumps out and captures it with it's clawed front feet.  After the prey is captured, they use their sharp beak to pierce and inject digestive enzymes into it. ( 2012)  This breaks the organism down in to a liquid-like substance that can then be easily ingested.

Photo credit: Jason Neuswanger,