Important wavelengths can be determined from PLS regression coefficients and difference in spectra

"The wavelengths important in classifying the species of interest were determined based on PLS regression coefficients and differences in spectra."

"The regression coefficients indicating important wavelengths in the calibration model are shown in Fig. 1."

(Fengyou, J., Maghirang, E., Dowell, F. Abel, C. and Ramaswamy, S., 2007. Differentating tobacco budworm and corn earworm using near-infrared spectroscopy, Journal of Economic Entomology, Vol. 100, No. 3, 759-763.)