Abstract: Ultrastructure of the indirect flight muscle of cotton bollworm Helicoverpaarmigera (Htibner) moth was investigated with electron microscope. The polygonal,close-packed elliptical myofibrils consist of 4004800 myosin filaments. Thick and thin filaments form a hexagonal lattice with the thin filaments midway between the adjacentthick filaments with actin and myosin in 3: 1 ratio. The sarcomere length is about 2.043.5 gm and the mitochondria are estimated to be about 42.38-48.57% of the fiber's total volume. The development of myofibril and mitochondria had fulfilled after emergence, while the development of T-tubules is relatively slow, and they mature after the third day of moth eclosion and occupy 3. 31%-3.54%of the muscle volume in 5 day-old moth. No significant difference is found between flight muscle structures of experimental population and migratory moths collected on Bohai Sea where is about 80 Km away from the continent, but the mitochondria in migratory moth showed many cavitiesprobably caused by energy exhaustion of flight.

Key words: Helicoverpa armigera, flight muscle, ultrastructure