Plausible pathways for water and solutes in cocoon fluids, body fluids and stream water. 5A: Under normal conditions, stream water is forced into the cocoon fluids due to the large osmotic gradient across the semi-permeable membrane. As the prepupae moult, exuvial fluids rich in ions are released and the cocoon fluids are gradually diluted. The pupae might excrete excess water from their bodies into the cocoon fluids. 5B: In high-temperature water, the rate of water influx into the cocoon fluids may decrease because the reduced flow is associated with less precipitation to enrich the stream water’s solute concentration. High and fluctuating water temperatures and low pH might also influence the physical and physiological properties of the cocoon and pupa, resulting in cocoon shrinkage.