predaceous aquatic insect that swims on its back and may inflict painful bites

predaceous aquatic insect that swims on its back and may inflict painful bites

predaceous aquatic insect that swims on its back and may inflict painful bites

one of a series of slit openings in the pharynxes of fishes and aquatic amphibians through which water passes

one of a series of slit openings in the pharynxes of fishes and aquatic amphibians through which water passes

prolific South American aquatic weed having grasslike leaves and short spikes of white flowers; clogs waterways with dense floating masses

prolific South American aquatic weed having grasslike leaves and short spikes of white flowers; clogs waterways with dense floating masses

prolific South American aquatic weed having grasslike leaves and short spikes of white flowers; clogs waterways with dense floating masses

prolific South American aquatic weed having grasslike leaves and short spikes of white flowers; clogs waterways with dense floating masses

prolific South American aquatic weed having grasslike leaves and short spikes of white flowers; clogs waterways with dense floating masses