The oriental armyworm Mythimna separata (Walker) is a long distance migratory insect. It is well known that occurrence of this insect migratory behavior is regulated by many environmental and physiological factors such as rearing temperature, larval density, photoperiod, matting status, oviposition and hormone, while little is known affected by genetics. Since migration in insects usually occurs prereproductively and so the pre-oviposition period, determines the number of nights over which females of migran...