Ambush, or sit-and-wait, predation is a tactic used by both vertebrates and invertebrates. Though this is a common predation strategy, the sensory cues that trigger an ambush strike are poorly understood in many ambush performing systems. One such system, the belostomatids (known as water bugs or toe-biters), cryptically wait in the vegetation of lentic systems (i.e. vernal pools, ponds, lakes) for an appropriate target to strike, restrain, and consume. We tested the strike response to artificial prey stimuli (black glass beads) using two North American belostomatid species, Belostoma flumineum and Lethocerus americanus. We found that the smaller species (B. flumineum) reaches its maximum strike probability when presented with 2.9 mm diameter beads (12% of body length), whereas the larger species (L. americanus) will strike objects between 10mm and 35 mm diameter (58% of body length) with similar maximum probability, indicating less of a discrete preference for prey size. The difference in strike response between the two species provides a paradigm for probing how sensory systems are tuned to elicit similar behavior responses to different stimuli. To test for differences in specialization at the level of the sensor, we used microCT and morphometric light-microscopy methods to determine the visual acuity of the two species. We hypothesized that the visual system of each species optimally resolves an image of the given size and distance matched to the animal’s maximum strike probability behavior. Future research will probe mechanisms of target selection in other sensory dimensions (i.e. mechanoreception) as well as at the level of the nervous system.