Chaff (the outermost protective layer of rice grain) in nano and ground sized particles was bio-assessed to explore its insecticidal effects against the greater wax moth, Galleria mellonella (Lepidoptera: Pyralidae). These particles induced remarkable disturbances in the biological patterns of the greater wax moth. These were cleared as they exhibited insecticidal impact on both juvenile and adult stages, their impacts on larval, pupal and adult death, the formation of morphogenetic features (permanent larvae and larval-pupal intermediates), their negative influence on the adult emergence and the potentialities of the applied concentrations to hinder the larval weight gain. The recorded LC50 values proved more larvicidal potency of the nano-sized particle than that of the ground rice chaff one. The transverse sections in the midgut of the 20 days old larvae (both treated and untreated ones) confirmed the histopathological deformations of the examined particles. The high siliceous content of the chaff particle may be responsible for such recorded disturbances.