Water depth can affect how N. glauca pick which prey they eat.
Males and females both spend a lot of time on the surface of the water where they encounter 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.
Mature females, however, will dive to the bottom of the pond to reach Asellus larvae, 
but only in shallow waters.
To reach the Asellus larvae there is an increase in the energy used in travel cost (diving) to reach this prey.
This behaviour is not consistent with the Optimal foraging theory.
It is possible, however, that because mature females are larger than males and immature females, they will have a reduced buoyancy and therefore reduce the energy needed to capture Asellus.
Also, mature females have a larger abdominal size, which could support a larger air bubble and allow them to remain submerged for longer.
However, if the water depth deepens, mature females will switch and spend more time at the surface and not feed on Asellus, as the deep water will increase the amount of energy needed for diving and staying submerged.
The amount of oxygen concentration in the body of water can affect the choice of prey N. glauca pick, as Cockrell (1984), found that when oxygen was at a high dissolved level, N. glauca will spend more time submerged and attacking Asellus.
Water depth can affect how N. glauca pick which prey they eat. Males and females both spend a lot of time on the surface of the water where they encounter 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. Mature females, however, will dive to the bottom of the pond to reach Asellus larvae, 
but only in shallow waters. To reach the Asellus larvae there is an increase in the energy used in travel cost (diving) to reach this prey. This behaviour is not consistent with the Optimal foraging theory. It is possible, however, that because mature females are larger than males and immature females, they will have a reduced buoyancy and therefore reduce the energy needed to capture Asellus. Also, mature females have a larger abdominal size, which could support a larger air bubble and allow them to remain submerged for longer. However, if the water depth deepens, mature females will switch and spend more time at the surface and not feed on Asellus, as the deep water will increase the amount of energy needed for diving and staying submerged. The amount of oxygen concentration in the body of water can affect the choice of prey N. glauca pick, as Cockrell (1984), found that when oxygen was at a high dissolved level, N. glauca will spend more time submerged and attacking Asellus.
Notonecta glauca