This study investigated the potential of a fluorescein-5 isothiocyanate conjugated-chitin-binding domain (FITC-CBD) probe to detect chitinous materials in the peritrophic membrane (PM) structure of the Japanese pine sawyer beetle, Monochamus alternatus. Results through direct observations indicated that the fluorescent probe specifically bound to chitin, and specifically labeled the chitinous materials in the PM. Applying the probe was easy, as fluorescence was stable, and the excitation maximum of the structures stained with the probe was within a range covered by most existing fluorescence microscopes. These advantages make fluorescence staining an easy method of choice for specifically visualizing the chitin-rich internal structures of insects. Additionally, this simple approach might have the added advantage of revealing chitinolysis events in vivo and in vitro.