Permeability of Insect Cuticle to Water and Lipids.

Insect cuticle presents a paradox: permeability to water may vary at different times, while lipids penetrate readily. Electron microscopy shows that the epicuticle is penetrated by filaments of wax 60 to 130 A in diameter. These are believed to be lipid-water liquid crystals in the middle phase. The variable permeability to water, and other properties of the cuticle, may be due to phase changes.