Poisonous moth caterpillar: 'do not touch it'
8 May 2013 Last updated at 12:10 BST
A poisonous moth caterpillar is on the increase in some parts of the UK, having been found in South London and Berkshire.
The oak processionary caterpillars can cause allergic reactions because each insect is covered with thousands of toxic hairs, which can cause irritation to eyes and throats and skin rashes.
Alison Field from the Forestry Commission told BBC Radio 5 live's Breakfast that if people find the caterpillars over the summer they "should not touch it".