Emergency Listing of the Miami Blue Butterfly as Endangered, and Emergency Listing of the Cassius Blue, Ceraunus Blue, and Nickerbean Blue Butterflies as Threatened Due to Similarity of Appearance to the Miami Blue Butterfly: Emergency rule.

We, the Fish and Wildlife Service (Service), exercise our authority pursuant to section 4(b)(7) of the Endangered Species Act of 1973, as amended (Act), to emergency list the Miami blue butterfly (Cyclargus thomasi bethunebakeri) as endangered. This subspecies is currently known to occur at only a few small remote islands within the Florida Keys. Current population numbers are not known, but are estimated in the hundreds of butterflies. We are also emergency listing the cassius blue butterfly (Leptotes cassius theonus), ceraunus blue butterfly (Hemiargus ceraunus antibubastus), and nickerbean blue butterfly (Cyclargus ammon) as threatened due to similarity of appearance to the Miami blue, with a special rule pursuant to section 4(d) of the Act. Due to the subspecies' severe reduction in geographic range, small population sizes, and imminent threats, we need to make protective measures afforded by the Act available to the Miami blue immediately. This emergency rule provides Federal protection pursuant to the Act for a period of 240 days. A proposed rule to list the Miami blue butterfly as endangered and to list the cassius blue butterfly, ceraunus blue butterfly, and nickerbean blue butterfly as threatened due to similarity of appearance to the Miami blue is published concurrently with this emergency rule, and it can be found in this issue of the Federal Register in the Proposed Rules section.