Please take care as Oak Processionary Moth Caterpillars have been found on Hampstead Heath. They can affect the health of both humans and animals.
The oak processionary (Thaumetopoea processionea) is a moth whose caterpillars can be found in oak forests, where they feed on oak leaves, causing significant damage. They travel in nose-to-tail processions (hence their name), often arrow-headed, with a leader followed by rows of several caterpillars abreast. They are a human irritant because of their venomous setae (hairs), which can cause skin irritation and asthma.