Life cycle of Tropidothorax cruciger(Motschulsky) was studied on Cynanchum wilfordii Hemsley in the field as well as its development, overwintering patterns, and host preferences. Overwintered adults appeared in early and mid May, and the first generation adults emerged from late June extending to mid August. Second generation adults which usually overwinter, appeared from mid September to early October and were usually found beneath the soil surface or fallen leaves in winter. Adults were not attracted to various light sources. T. cruciger showed host preferences specifically toward Metapiexis japonica and Cynanchum wilfordii, both in the family of Asclepiadaceae.