Oak processionary moth
Thaumetopoea processionea
- Group
- Stinging-hair caterpillar
- Risk
- Very high danger
- Protection status
- Not protected
- Identifying features
-
- Caterpillar with red-brown warts and long white hairs
- From the third larval stage onwards, microscopic stinging hairs containing the toxin thaumetopoein
- Grey silken nests on oak trees
- Night-time processions
The oak processionary moth (Thaumetopoea processionea) is one of the most hazardous caterpillar species in Switzerland in terms of health. This profile shows how to identify the caterpillar and its nest — for detailed information on how to deal with an infestation, see our oak processionary moth guide.
Identifying features
- Caterpillar: covered in distinctive red-brown warts and long white hairs
- Stinging hairs: from the third larval stage onwards, microscopically fine stinging hairs containing the toxin thaumetopoein develop
- Nest: dense, grey silken nests on oak trunks and branches
- Behaviour: night-time processions in long single-file lines between the nest and the feeding site
Risk
Very high: on contact, or when blown through the air, the stinging hairs trigger what is known as caterpillar dermatitis, with skin irritation and eye and respiratory complaints. Even abandoned nests remain toxic for up to 12 years.
Protection status in Switzerland
The oak processionary moth is not legally protected in Switzerland.
What to do about an infestation
Because the stinging hairs pose such a high health risk, nests should never be removed by yourself. We explain the correct approach to an infestation in our oak processionary moth guide.