Abstract:Dynamics of energy reserves and utilization after flight in the beet armyworm, Spodoptera exigua, were investigated. Dry body weights were highest on day 2 after emergence. Glyceride level in the newly emerged males was significantly lower than that of males of days 2-5 after emergence; glyceride contents in females shared a similar trend to that of males except that glyceride content on day 4 was significantly lower than those of other days. Glycogen contents in females increased sharply from newly emergence to day 2 and then decreased slowly but increased again at day 5. In males, glycogen contents increased rapidly from emergence to day 1, and then fluctuated on the subsequent days. Consumption of energy reserves during flight differed between different days after emergence. Flights on day 2 after emergence utilized a significant amount of glyceride and glycogen. But a 48h tethered-flight starting from day 1 or day 4 consumed an insignificant amount of glycogen, meanwhile, a 48h tethered-flight starting from day 1 or day 4 consumed a significant amount of glyceride except for females starting flight on day 1. These results showed that the beet armyworm can use both glyceride and glycogen as fuel for its flight.