Morphological changes induced by thermal treatment and gamma irradiation on the males' hind legs of Spodoptera littoralis (Noctuidae; Lepidoptera)

External morphology of males' hind legs of Spodoptera littoralis subjected to thermal treatment (33 °C and 37 °C) or/and irradiated with substerilizing doses of gamma radiation (75, 100 and 150 Gy) were studied using scanning electron microscopy (SEM) in the parental generation. Five types of sensilla have been distinguished; three types of trichoid sensilla (T1,T2 and T3), sensilla basiconica and sensilla auricillica, which are considered as olfactory chemoreceptors. Moreover, sensilla chaetica are contact chemoreceptors, whereas sensilla styloconica are thermo–hygro/gustatory mechanoreceptors. The impact of thermal treatment or/and gamma irradiation reflect a clear morphological change in S. littoralis legs'sensilla, claws, spurs and scales. Otherwise, the degree of deformity was thermal and dose dependent, as it increased with an increase of the degree of temperature and dose of irradiation applied. Substerilizing doses 75 and 100 Gy, either alone or combined with thermal treatment 33 °C, have low undesirable effects on the hind legs with successful mobility or courtship behavior. Consequently, synergistic effect of gamma radiation and thermal stress induced successful application in the integrated pest management program for controlling S. littoralis.