Lytta aenea, commonly known as the Spanish fly, is a species of blister beetle found in Europe and parts of North Africa. It is a metallic green insect with a length of about 10-20 mm. The Spanish fly is known for its potent defensive secretion, cantharidin, which is used in traditional medicine and has historically been used as an aphrodisiac, although it is highly toxic and can cause severe blistering if mishandled.