Pupillary response under varying conditions of bright light and darkness was compared in three species of Cubozoa with differing ecologies. Maximal and minimal pupil area in relation to total eye area was measured and the rate of change recorded. In Carukia barnesi, the rate of pupil constriction was faster and final constriction greater than in Chironex fleckeri, which itself showed faster and greater constriction than in Chiropsella bronzie. We suggest this allows for differing degrees of visual acuity between the species. We propose that these differences are correlated with variations in the environment which each of these species inhabit, with Ca. barnesi found fishing for larval fish in and around waters of structurally complex coral reefs, Ch. fleckeri regularly found acquiring fish in similarly complex mangrove habitats, while Ch. bronzie spends the majority of its time in the comparably less complex but more turbid environments of shallow sandy beaches where their food source of small shrimps is highly aggregated and less mobile.