The individuals of a lycaenid butterfly, Lycaeides argyrognomon in Ueda city, Nagano prefecture were founded in 2011 that the larvae ate Melilotus officinalis alba which was a naturalized plant, and that grew up(Tashita et al.,2013). The adaptation of the feeding habits to Melilotus officinalis alba of a lycaenid butterfly, Lycaeides argyrognomon was investigated by comparing the growth condition of the larvae with the individuals in Matsumoto city, Nagano prefecture, that the larvae didn't eat Melilotus officinalis alba. As the result, the survival ratio of the Ueda and Matsumoto individuals on Melilotus officinalis alba was each 0.0 % at indoor breeding during summer period (Ueda n= 23, Matsumoto n= 32), and was each 0.0 % (n= 19.5) and 11.5 % (n= 34.7) at indoor breeding during autumn period. The difference of the survival ratio was not accepted between both individual groups. Furthermore, during from eggs to pupation on Melilotus officinalis alba, it became 39.0days(n=l) in the Ueda individuals at indoor breeding during summer period (not pupation in the Matsumoto ones) to 21.9±2.29days(n=7) on Indigofera pseudo-tinctoria, and 65.0±11.25days(n=4) in the Matsumoto individuals at indoor breeding during autumn period (not pupation in the Ueda ones) to 51.3±10.34days(n=3) on Indigofera pseudo-tinctoria. The growth period of the both Ueda and Matsumoto individuals on Melilotus officinalis alba became the rather longer than the period on Indigofera pseudo-tinctoria. Therefore, it was not accepted that feeding-habits of the Ueda individuals converted to Melilotus officinalis alba.