Notonecta glauca, also known as the greater water-boatman or common backswimmer, is a species of aquatic insect in the family Notonectidae.

This species is found in large parts of Europe, North Africa, and east through Asia to Siberia and China.

These insects use their eyes for both day and night vision, which is used for prey capture and flight when searching for new habitats.

Specifically, their eye is an acone-type with corneal structure, which helps them create a sharp image when both in the water and in the air.

To protect their eye from direct sunlight during the day, the pigment cell's diaphragm are condensed, and during the night they open fully to allow as much light in as possible.

[5] Notonecta glauca pupil (acone) take a different amount of time to adjust to light.

When these insects are diving or resting under the water surface, they create a film of air that surrounds their body.

Males and females both spend a lot of time on the surface of the water where they encounter mosquito (Culex) larvae.

They feed on this prey because there is a decrease in travel cost (having to dive for them) and Culex gives a higher energy rate.

[19] Mature females, however, will also dive to the bottom of the pond to feed on isopods (Asellus), but only in shallow waters.