Effect of photoperiod and 20-hydroxyecdysone on post-embryonic development and diapause disruption in Cirina butyrospermi Vuillet (Lepidoptera: Saturniidae) under laboratory conditions

Abstract Cirina butyrospermi (Lepidoptera: Saturniidae), commonly known as the shea caterpillar, is an edible insect in several West African countries. However, this insect is seasonal due to a long pupal diapause. This study therefore aims to explore the potential for mass rearing of C. butyrospermi by determining the role of photoperiod and 20-hydroxyecdysone in disrupting or shortening diapause. Exposure of larval growth to different photoperiod conditions, i.e. L.D. 6:18, L.D. 8:16, L.D. 10:14 and L.D. 12:12, affected larval weight and adult emergence. With respect to the photoperiod treatments applied to larval growth from neonate to fourth instar, caterpillars reared under L.D. 6:18 conditions weighed more than those reared under the other photoperiods. However, photoperiod treatments did not significantly affect the pupation rate. Adult emergence was only observed under L.D. 6:18 photoperiod conditions for a diapause average duration of 140.85 days. The recorded emergence percentage was 38.46 ± 1.33%, and emergences occurred over a period of ten days. When the L.D. 6:18 photoperiod conditions were applied only on the fourth instar larvae, 24.39 ± 1.41% of pupae developed to adults in 34.50 days on average and emergences were grouped in 4 days. Injections of increasing doses of 20-hydroxyecdysone into diapausing pupae resulted in diapause breaking within 23-28 days in 7-47% of treated pupae, depending on the dose of 20-hydroxyecdysone and the pupal weight. Conversely, diapause remained in non-treated pupae during the study period. Short photoperiod and 20-hydroxyecdysone are key drivers for diapause termination in C. butyrospermi . The possible interaction between 20E doses and treated pupae weight provides new insights into the hormone’s efficacy in breaking pupal diapause in C. butyrospermi . While the results need further clarification, they represent a significant step towards mass breeding of this important food insect.