Effects of larval diets on flight capacity and flight fuel in adults of the common cutworm, Spodoptera litura (Lepidoptera: Noctuidae)

The last instar larvae of Spodoptera litura were reared on soybean leaves (SL), eddo leaves (EL), an artificial diet (AD), or AD supplemented with soybean oil (AD+O). Larvae fed on SL developed faster into adults with smaller sizes and lower levels of triacylglycerol (TG) than those from the AD or AD+O groups. The ratio of C18 unsaturated fatty acids in the TG fatty acids was similar (nearly 40%) among the adults of these three groups, as was the average total flight duration of about 6 h tested over 20 h of tethered flight. The ratio of C18 unsaturated fatty acids in the TG fatty acids tended to decline with longer tethered flight in the adults of these three groups. On the other hand, the development of individuals from EL was greatly retarded and they emerged as the smallest adults with the lowest level of abdominal TG with essentially no C18 unsaturated fatty acids in the TG. Adults from EL could barely fly when tested in tethered flight. These results support the notion that the flight capacity of S. litura depends greatly on the plants eaten as larvae and the C18 unsaturated fatty acids in the TG function as the major flight fuel.