Anyone out walking in Jersey is being asked to keep clear of any Oak Processionary Moth.
The caterpillars that nest on oak trees have been spotted in St Catherine's Woods.
People who touch them can get a very uncomfortable skin reaction.
Jersey Trees for Life has issued a warning with photos an islander that developed a rash last week.
Anyone who sees them should report it to the Environment Department.

UK group takes over Channel Island Costa Coffees
New Jersey-owned restaurant set to take over former Pizza Hut site
Election votes could be counted the next day
First-year update on Jersey Electricity's £120 million upgrade
22 year old walks the length of Ireland for three charities
'Shame on you': Havre Des Pas Lido protesters take to the Royal Square
Breath tests for skippers suspected of careless driving in Jersey waters
'Dream come true' England call-up for Guernsey's Alex Scott