The armyworm, Mythimna separata (Walker, 1865) (Lepidoptera: Noctuidae), is a global migratory pest of crops. This migratory pest’s details study has been continuously followed by different researchers for a long history, factors that affecting the wingbeat frequency (WBF), as the insect is migratory, which mainly related to flight activity of the armyworm, remain Mistry and unclear. During the study, the WBFs of cultured and migrating moths both were observed carefully and tested under different natural and created conditions in the laboratory using the stroboscope. With the observation the study indicated efficiency of conversion of ingested food. These findings about the armyworms provide a deeper and useful understanding of factors that mainly affect conversion of ingested food in M. separata, which will be helpful for the researcher and other investigators to developing a regional migratory monitoring system through which they can develop a warning system of the pest, which can help in identifying target insect species based on.