They may look fluffy and harmless but nature lovers are being advised to avoid these creepy crawlies which are a health hazard to people, animals and trees.
Friends of Mitcham Common are warning regular walkers about Oak Processionary Moth caterpillars.
The caterpillars have tiny hairs which can be blown about to cause itchy skin rashes, eye and throat irritations and occasionally breathing difficulties in people and animals.
A spokesman for the organisation said: "Definitely don’t touch them, even better to stay well away from them!"
Picture: Gristwood and Toms
The Oak Processionary Moth caterpillars, above, are so named because of the way cluster together and move in nose to tail processions and live almost exclusively in oak trees.
The greatest risk period is May to July, but nests should always be avoided because they can contain thousands of hairs the caterpillars have shed.
The furry insects are a native species of southern Europe and were introduced to Europe by accident.
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