MONITORING OF RICE WEEVIL, SITOPHILUS-ORYZAE, FEEDING-BEHAVIOR IN MAIZE SEEDS AND THE OCCURRENCE OF SUPERNUMERARY MOLTS IN LOW HUMIDITY CONDITIONS

Rice weevils, Sitophilus oryzae (L.), complete their development from egg to early adulthood inside grains of wheat, rice or maize, but litt le is known about their feeding behavior within the seeds. An ultrason ic insect feeding monitor was used to characterize the feeding pattern s of individual rice weevils as they developed in maize grains. Weevil s reared in grains held at ca. 40% r.h. took longer to develop from eg g to pupation than those reared in grains kept at ca. 70% r.h. Feeding patterns revealed that larvae developing in grains held at ca. 70% r. h. had only four instars, whereas supernumerary molts (five instars) o ccurred in certain individuals reared in grain held at ca. 40% r.h. Th e supernumerary molts may represent a response of the insect to stress es associated with low moisture levels in the seeds.