Recalling a figure from an earlier discussion, we review the potential effects of osmotic imbalance. Cells placed in an environment of far higher salt concentration than themselves often lose water, becoming shrunken and deformed. To the other side, cells placed in an environment of far lower salt concentration than themselves often gain water, even to the point of bursting. Again, maintaining an osmotic balance is important to survival of organisms. The situation for aquatic insects is easy to apprehend.
Insects living in fresh water are generally hyperosmotic to their environment.
Under this condition water tends to diffuse into aquatic insects. If left unattended this process would effectively place cells in a very dilute environment. Insects living in salt water, such as brine flies, are generally hypoosmotic to their environment. These insects tend to lose water to the environment. Again, if left unattended, this would put the cells within the insect in a state of water loss and shrinkage.