Dietary effect of sugarcane juice and glucose on the adult black soldier flies lifespan (Diptera: Stratiomyidae)

The study aimed at enhancing adult Hermetia illucens (Linnaeus, 1758) lifespan and oviposition by using a range of liquid diet solutions. Adult black soldier flies (BSF) have a short lifespan ranging 7–9 days when given only water during rearing. In order to increase their lifespan, alternative energy-rich liquid diet solutions need to be introduced to the flies. In this study, water (control), milk, sugarcane juice and glucose were used. A total of 100 newly emerged 4-day-old flies were introduced into rearing cages and maintained under a 12:12 light/dark cycle. Each dietary treatment was replicated three times, with 110 ml of each liquid diet provided to flies through soaked cotton wool. The flies were reared under optimum temperature (28.62  ±  4.38 °C) and relative humidity (66.27 ± 10.48 %) conditions. Significant differences in the BSF lifespan and oviposition rates were observed, p<0.001. Sugarcane juice diet was associated with the highest survival rate (94.00 ± 0.02 %) and oviposition (43 552 ± 2504 eggs), and the lowest values (73.00 ± 0.04 % and 6584 ± 2896) were observed under the water diet. Glucose and sugarcane juice doubled the fly lifespan to 14 days. Significant differences in the hazard ratio with reference to the water diet were noted, p<0.001. Glucose and sugarcane juice showed the lowest risks, with hazard ratios of 0.013 and 0.034, while the milk diet was associated with the highest hazard rate of 0.322. Sugarcane juice and glucose slow down the fly mortality, thus offering the best survival and high oviposition advantage. Our results show that utilisation of energy-dense diets such as glucose and sugarcane juice increase the lifespan of adult BSF populations.