Technical Abstract: Neomusotima fuscolinealis Yoshiyasu was discovered to feed on and damage the leaves of Lygodium japonicum (Thunberg ex Murray) Swartz, an invasive weed in Florida and the southeastern U.S., in its native Japan. Larvae and pupae of the moth were imported into the quarantine facility at the Florida Biological Control Laboratory, Gainesville, Florida to establish a colony to conduct preliminary host range studies and to define its lifecycle and reproduction parameters. Larvae of the moth did not feed significantly nor develop on five tested rare, native Florida ferns. The rare North American native climbing fern, Lygodium palmatum (Bernhardi) Swartz, however, supported complete development of N. fuscolinealis, and six continuous generations of the moth were reared on the fern. Because the rare L. palmatum and the invasive L. japonicum co-occur in the US, the release of N. fuscolinealis could result in the harm to L. palmatum, a risk that determined the moth to be unsuitable as a potential biological control of L. japonicum.