The larvae can cause allergy-like symptoms
Work is being undertaken to prevent the spread of a moth in south-west London which is potentially harmful to humans.
Experts want to destroy the larvae of oak processionary moths which has been found on trees in Richmond over the past two summers.
The distinctive hairy caterpillars and their nests are expected to begin appearing towards the end of the month.
Contact with the creatures can cause itching, rashes, conjunctivitis and, in some cases, breathing problems.
As part of the work by Richmond council oak trees across the borough will be examined and residents are urged to report any sightings on private land.
The caterpillars feed on leaves and produce silken nests on the trunk or branches of oak trees.
They are named after their habit of forming nose-to-tail processions on the trees.
People are warned not to handle the creatures, remove or disturb the nests as the hairs contain a toxin which causes allergy-like symptoms.
Councillor Martin Elengorn, said: "While there is no cause for alarm, the caterpillars can cause unpleasant symptoms in anyone who comes into contact with their hairs.
"If left unchecked they can also do considerable damage to oak trees."
The council is being advised by experts from the Forestry Commission and the Royal Botanic Gardens in Kew.