Fluorescence from the wings of male Morpho sulkowskyi and Papilio xuthus butterflies has been investigated for the first time using time-resolved fluorescence spectroscopy. Intensity of emission spectra from the wings of Papilio xuthus decreased with increasing delay time after the application of exciting laser pulse and the intensity peak showed an interesting red shift from 480 to 520 nm. In contrast, such a peak shift was not observed from the wings of Morpho sulkowskyi. The decay times obtained from the wings of Morpho sulkowskyi and Papilio xuthus were given by two components, respectively; those of the former at 510 nm were about 0.545 ns and 2.74 ns and those of the latter at 480 nm were about 0.490 ns and 2.10 ns. Based on these results, the possibility of using time-resolved spectroscopy as a tool for the classification of butterflies is described along with a brief discussion of the origin of the 520 nm peak observed for Papilio xuthus.