Photinus cookii is a species of firefly in the beetle family Lampyridae. It is found in North America in the Eastern USA, including Florida and Texas.
Etymology
The species was first described by John Wagener Green in 1956. The species is named as an honorific for Mr. Carl Cook, who had collected the holotype male and other specimens in Carilhope, Kentucky, 11-VII-1946. The species name is therefore noun in genitive case.
Several years later Lloyd (1966) published an overview of Photinus in USA, and wrote the name as "Photinus cooki" (i.e. altering the ending to a single "i" as "cooki"), perhaps considering it as a correction; but per nomenclatural regulations in ICZN 31.1, the original spelling of "cookii" is admissible and therefore it is subsequently retained.