n African Entomology - Improved techniques for mass-rearing (Lepidoptera : Noctuidae) on an artificial diet

Volume 9, Issue 2
  • ISSN : 1021-3589



Techniques are described for the continuous rearing of (Fuller) (Lepidoptera : Noctuidae) on an artificial diet. The insect was reared for 20 successive generations at 25 °C, 85 % RH and photoperiod 12 : 12 h. The larval stage lasted on average 27.6 days for males, and 28.5 days for females. The pupal stage lasted on average 13.4 days in both sexes, and mean total development time (egg to adult) was approximately 50 days. The mean pupation rate was 80 %. Adult emergence rate was 74 %, with a mean sex ratio of 1 : 0.9. Females laid an average of 514 eggs of which 52 % hatched. Additional experiments were conducted to develop techniques to improve oviposition by moths, and to manipulate larval, pupal and egg incubation times. Mating and hatching rates were similar with wooden-framed cages containing 35 males : 30 females and plastic, bottle cages with 4 males : 3 females used in the routine rearing. Pupation was delayed by 16 days when larvae were kept at 20 °C instead of 25 °C; adult emergence was delayed by 8-27 days when pupae were kept at 15 °C instead of 25 °C; and hatching of eggs was delayed by 3-7 days when eggs were kept at 15 °C for 7-9 days instead of 25 °C. Studies on larval diapause termination indicated that diapause could be manipulated to provide pupae and moths for use in the mass-rearing colony. The optimum pupation rate (70 %) was obtained by watering diapause larvae daily for six days (compared to 40 % pupation rate for larvae receiving no water), with pupae forming over a mean period of 12.3 days (compared to 43.9 days to pupation for larvae receiving no water).

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