Two young thunder-gods, sons of the chief thunder-god, fell violently in love with the same Aino woman. Said one of them to the other, in a joking way: "I will become a flea, so as to be able to hop into her bosom." Said the other: "I will become a louse, so as to be able to stay always in her bosom."

"Are those your wishes?" cried their father, the chief thunder-god. "You shall be taken at your word"; and forthwith the one of them who had said he would become a flea was turned into a flea, while he who said he would become a louse was turned into a louse. Hence all the fleas and lice that exist at the present day.

This accounts for the fact that, whenever there is a thunder storm, fleas jump out of all sorts of places where there were none to be seen before.