The Japanese jewel beetle (Chrysochroa fulgidissima) is one of the beautiful beetles showing metallic green color that is kept over a millennium. This is a typical structural color resulting from a multilayer, frequently seen in insects. It was found that the elytra unexpectedly change the color from original green to blue or red by heating at 200 degrees C or by immersing in bromoform for over I month. This variability implies that the multilayer consists of a thermosensitive porous ma- terial. The color change induced by heating was accompanied with elytron shrinkage; the sensitivity of the reflection peak was -0.6 nm/degrees C in 30-65 degrees C. The porous structure was determined by positron annihilation lifetime spectroscopy; the averaged pore radius was around 0.25-0.30 nm, which is close to the size of the bromoform molecule. These features prove the thermosensitivity and porous structure of the multilayer although in unusual environments. J. Morphol. 268:826-829, 2007. (C) 2007 Wiley-Liss, Inc.