Regulan bloodworm

The Regulan bloodworm (Regulani vermis) is a parasitic life form native to Regula II. (Star Fleet Medical Reference Manual)

Korax, a Klingon lieutenant, once insultingly compared Humans to Regulan bloodworms on Deep Space Station K-7 in a conversation which immediately preceded a barroom brawl. (TOS episode: "The Trouble with Tribbles")