What percentage of insect plasma is water?

• A. 70%
• B. 80%
• C. 90%
• D. 60%

Answer: (C)

Insect plasma, or hemolymph, is the fluid that bathes tissues in an open circulatory system. It is essentially an aqueous medium, meaning most of its volume is water. This high water content is what carries dissolved nutrients, ions, sugars, amino acids, hormones, and immune factors through the insect’s body. Across many insect species, the water fraction of plasma is about 90%, with the remaining ~10% made up of dissolved solids like proteins, lipids, and salts. That’s why 90% is the best answer—the plasma is predominantly water, not a solution rich in solids. If it were only 60–80% water, the plasma would be far less able to dissolve and transport these substances, which would impair circulation and metabolism.