The ability and accuracy of near-infrared spectroscopy (NIRS) to predict the chronological age of the rice weevil Sitophilus oryzae (L.), the lesser grain borer Rhyzopertha dominica (F.), and the red flour beetle Tribolium castaneum (Herbst) three of the most destructive pests of stored grain was examined. NIRS predicted age correlated well with actual age of the three species. Calibration models developed with mixed sex insects improved classification accuracy compared with results from calibration models developed by only males or females. Water content varied with age in rice weevils and excluding wavelengths at which water absorbs radiation slightly reduced the rate of correct classification. Removing cuticular lipids from insects resulted in a significant decrease (» 39%) in classification accuracy of weevils indicating that these compounds are likely responsible for the ability of NIRS to differentiate young and old beetles.
Species 1: Coleoptera Curculionidae Sitophilus oryzae (rice weevil)
Species 2: Coleoptera Bostrichidae Rhyzopertha dominica (lesser grain borer)
Species 3: Coleoptera Tenebrionidae Tribolium castaneum (red flour beetle)
Keywords: near-infrared spectroscopy, cuticular lipids
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