Sericinus montela,a globally threatened butterfly species, feeds exclusively onAristolochia contorta(Northern pipevine).Field surveys and glasshouse experiments were conducted to obtain a better understanding of the relationship between the two species. Interviews with the persons concerned withA. contortawere conducted to collect information about the site management measures. We found that management practices to control invasive species and manage the riverine areas might reduce the coverage ofA. contortaand the number of eggs and larvae ofS. montela. Our results indicated that the degraded quality ofA. contortamay result in a decrease inS. montelapopulations by diminishing their food source and spawning sites. This study implies that ecological management in the riverine area should be set up to protect rare species and biodiversity.