Biochemical content in fatty acids and biological parameters of Harmonia axyridis reared on artificial diet

A flightless strain of Harmonia axyridis (Pallas) (Coleoptera Coccinellidae) was fed, at the larval and/or adult stage, on a liverbased artificial diet supplemented with lin-seed oil, which is rich in α-linolenic acid (C18:3n-3), an essential lipid for the fecundity of different insect species, and other unsaturated fatty acids. Biochemical analyses revealed that, compared to Ephestia kuehniella Zeller eggs (the control food for H. axyridis), the diet content of C18:3n-3 was higher (P < 0.05), whereas the content of linoleic acid (C18:2n-6) was not significantly different (P > 0.05). The composition in fatty acids of H. axyridis newly-emerged females, which were fed on the artificial diet during the larval stages, reflected the composition of the diet. In particular, these females showed a higher concentration of α-linolenic acid compared to control females. Moreover, no difference was found for total fatty acids between the control newly emerged females and those reared as larvae on the artificial diet. On this diet, fecund H. axyridis adults were obtained, but the emergence rates and a number of quality parameters (including the development times, the weights of the newly-emerged adults, the female fecundity and fertility) of the diet-fed H. axyridis were worse compared to the coccinellids fed on E. kuehniella eggs. The diet may however be utilized for adult maintenance, in order to reduce production costs, or in case of shortage of aphids or E. kuehniella eggs.