The "little sails" in Puerto Soller. | Lluc Garcia

Although it is a not uncommon occurrence in the Balearics, the appearance of thousands of "velella velella" washed up on beaches can still cause a surprise. This was the case in Puerto Soller on Monday, when the beaches were covered with them. As they were decomposing, the smell started to increase. Beach-cleaning services removed them.

The velella velella, blue in colour, has different names - sea raft, by-the-wind sailor, little sail. It comes from the same family as the Portuguese man o' war, so isn't, strictly speaking, a jellyfish. It floats on the sea surface and its appearance on beaches, in hundreds or thousands, depends on currents and wind direction. The phenomenon in Soller is indicative not just of these circumstances but also of the arrival of spring.

Unlike the Portuguese man o' war it is relatively harmless. It can cause itching, however, so contact with the skin is not recommended.