Every summer, jellyfish return to many of the world's coasts. However, the phenomenon observed this year in Massachusetts, in the United States, far exceeds the usual episodes. Thousands of lion mane jellyfish (Cyanea capillata), considered to be the largest in the world, have been reported on several beaches. Their spectacular size attracts attention, while their tentacles loaded with hives represent a real danger for bathers, fishermen and eve…