Experts on the spider crabs seen swarming beaches in Cornwall in recent weeks have issued an urgent clarification about the creatures.
The army of crabs, recognisable for their long legs and pincer claws, have been spotted in the shallow waters.
The swarm had led to fears they are venomous to humans and to avoid at all costs.
But experts now say that is incorrect and they are harmless to people, Cornwall Live reported.
Matt Slater, marine conservation officer at Cornwall Wildlife Trust, said: “I’ve spent my whole career trying to get people to appreciate amazing marine animals like spider crabs.
“Reports of them being venomous are simply untrue and could damage their reputation. These animals are truly unique and are completely harmless to humans.
“Despite the many gatherings we’ve seen in places like St Ives, it’s not that common to witness this kind of behaviour. I saw it for the first time in Falmouth last year and it was an unbelievable experience.
“Please go out, enjoy our coastline responsibly and admire these sensational spider crab displays should you be so lucky to see one.”
There was confusion earlier this month as passers-by believed hundreds of crabs to be dead, when in fact it was just the shells shed by the crabs before returning to sea.
The confusion over the crabs’ toxicity is believed to have stemmed by the fact that crab spiders are venomous, while spider crabs are not.
Katie Maggs, a BSAC snorkel instructor and volunteer for Mounts Bay Marine Group who filmed one of the gatherings, added: “The spider crab mass moulting looked like something you’d see in a tropical country, yet it’s happening right here in Cornwall!
“I feel so lucky to have witnessed it first-hand.”
While it is not unusual to see them in UK waters, mass gatherings like this one are becoming more common in the summer due to rising sea temperatures.
Once the crabs grow another tough outer shell they will disperse to depths of 300ft and paddling will become far more appealing.
Spider crabs are popular around Cornwall and are often spotted by scuba divers in the area around the summertime. The unique crabs are known for their spiny legs and their claws can span up to one metre.
In recent years, the population of spider crabs seems to have grown. This is due to climate change and sea temperatures warming.
The population growth is expected to continue in years to come.