Sweden has a native species of brick-red forest slug, Arion rufus. The country has also recently acquired an invasive slug species that is likewise brick red, Arion vulgaris. Swedish people immediately forgot that A. rufus exists and started to exterminate all brick red slugs.
A Gothenburg study that asked people to send A. vulgaris specimens received 60% indigenous A. rufus. Because people just can't tell them apart.