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.

'Momentous' week in Jersey's States
Plans to charge wealthiest patients for medical travel
Railway Walk reopens 'several weeks' ahead of schedule
New bar opening at former Rojo and X site to evolve Jersey's nightlife
Former Chief Minister seeks re-election
Château Vermont to become home to new music campus
St Saviour break and entry suspect pictured posing on motorbike
'Overstretched' neurology department following under-experienced managers