Oak processionary caterpillars, Thaumetopoea processionea, have invaded London. These caterpillars have thousands of urticating hairs that can cause a painful rash and dermatitis. The hairs can be carried on the wind and cause symptoms in people who are in the vicinity of infested trees. The forestry commission in London has issued warnings for people to avoid the caterpillars and report them to authorities who will physically remove them.
Thaumetopoea processionea, has lived for years in Southern Europe where its populations are controlled by natural enemies (Parasitoids, Predators and Diseases) that keep populations in check. However, the warmer weather has allowed this caterpillar to move further north where it can escape its enemies and erupt into larger populations. This has adverse effects on people in more Northern areas, including US military personnel and their families who live on bases in infestation zones. Logan, Benenson and Moser discussed the problem in a 1999 article in Military Medicine (1999: Nov: 164(11):767-70) “Acute dermatitis from oak processionary caterpillars in a U.S. military community in Germany”. In the article they report over 150 cases of soldiers and civilians seeking treatment after exposure.
The recent northward push of the caterpillar is in part attributed climate change, as conditions in Northern Europe become more favorable. As our climate continues to warm, Entomologists anticipate many of the insect problems associated with more Southern areas to move north.