Poisonous caterpillars could be making their homes in Camden’s oak trees, the Forestry Commission has warned, advising residents not to touch the insect nests.

Ham & High: The poisonous oak processionary caterpillars. Picture: Forestry CommissionThe poisonous oak processionary caterpillars. Picture: Forestry Commission (Image: Archant)

The hairs of the distinctive spiny yellow and black oak processionary caterpillars contain an irritating substance called thaumetopoein, which can cause painful skin rashes as well as irritating the eyes and throats of people and animals.

Camden residents, along with visitors to the borough’s green spaces, such as Primrose Hill and Hampstead Heath, are being advised not to touch the bugs and to keep pets away from their white silky nests, which look like spiders’ webs from far away.

The pests, which damage oak trees by stripping them of their leaves, eventually grow into the oak processionary moth.

The nests, normally built in June, are about the size of a tennis ball and can become discoloured to match the colour of the oak tree’s bark. Although they usually hang on the tree, the nests can fall to the ground.

Royal Parks, which manages Primrose Hill, and the City of London Corporation, which runs Hampstead Heath, reported the caterpillars have not been sighted in the green spaces.

A Royal Parks spokesman said: “We have a rigorous control programme for oak processionary moths in order to protect tree health and biodiversity in the parks.”

A Camden Council spokesman said: “If anyone does find these nests, they should report them as soon as possible to pest control.”