Function of yeast extract in greater wax moth farming: does yeast extract always improve the development and reproduction of insects?

Abstract

The Galleria mellonella L. (Lepidoptera: Pyralidae) has great nutritional potential for humans and animals and is currently used as a model organism in many biological studies, despite its damage to the apicultural industry and wild honeybee colonies. Yeast extract that promotes insect development and reproduction by containing many necessary nutrients has always been an important yet expensive ingredient in the majority of artificial diets for G. mellonella. To better understand the influence of yeast extract content on G. mellonella mass-rearing, the life table parameters from G. mellonella mass-reared on increasing amounts of yeast (0% in control, 2, 4, 6, 7, and 9% of the total diet, respectively) under laboratory conditions were analysed according to age-stage, two-sex life table theory. Harvest rate and recruitment cost to produce 10,000 pupae were also assessed to help identify an economically sustainable rearing system. The intrinsic rate of increase (r) and finite rate of increase (λ) varied among diets. Highest values found in the G. mellonella population reared on a 9% yeast extract diet did not differ significantly from those of diets consisting of 4, 6, and 7% yeast extract, whereas these parameters were lowest in yeast-free artificial diets. The cheapest daily cost of rearing a population was 3,966.57 CNY (Chinese Yuan), and the heaviest pupal weight for both females and males (398.10±9.26 and 316.00±7.92 mg, respectively) were found with an artificial diet of 4% yeast extract. This study demonstrates that excessive dietary yeast extract is not always beneficial to G. mellonella. The most effective yeast extract percentage in G. mellonella mass-rearing diets is about 4% based on life table parameters, computer projection, and harvesting costs.