Abstract
The addition of fatty acids to drone honeybee brood powder (DP)-containing gel diet was found to improve larval development of aphidophagous syrphids, Episyrphus balteatus and Eupeodes bucculatus (Diptera: Syrphidae). When each fatty acid was added singly to the basic diet, the emergence rate was higher than on unsupplemented diets in E. bucculatus. In particular, the addition of oleic acid and linoleic acid improved the emergence rate and adult body size. The combination of both acids was most effective for the development of E. bucculatus. Two gel diets, consisting of DP, oleic acid, and linoleic acid at specific rates, were designed for young and old larvae, respectively; diet agar concentration was also specified. When these diets were provided to larvae of both species, these emergence rates exceeded 90% and adult body sizes were equivalent to aphid-fed controls. Three preservatives to stabilize diets were tested: propionic acid, sodium benzoate, and methyl paraben. Propionic acid (0.5%) had no effects on E. balteatus, but the emergence rate of E. bucculatus was much inferior to the control diet even at a concentration of just 0.1%.
