The public has been warned to be wary after colonies of Oak Processionary Moth caterpillars, Thaumetopoea processionea, have been sighted in several parts of London this month. The UK's Forestry Commission issued the warning about the caterpillars, which are native to southern Europe, after large colonies were spotted in several London boroughs as well as in the neighbouring counties of Berkshire and Surry. The caterpillars are covered in a dense coat of tiny hairs, which are covered in toxins that can cause skin complaints and respiratory problems, particulalrly in children, and which can achieve very high population densities in countries, such as the UK, where they have no natural predators.
Oak Processionary Moth caterpillars, Thaumetopoea processionea. Wikipedia.
Oak Processionary Moths are native to parts of Southern and Central Europe, where they have a number of natural predators. However a combination of a warming climate and accidental transplantation by Humans has led to the species becoming established in a number of countries in Northern Europe, where, in the absence of predators, they can form very large colonies, presenting problems for public health.
As well as the obvious problems caused by detect contact with the caterpillars, the detached hairs, which can remain toxic for up to a decade, can present problems in themselves. Each individual hair has very little toxin, and does not present any danger to Humans, but they hairs can become concentrated in places such as the surfaces of still ponds, or in the hoppers of lawnmowers, resulting in unexpected contact with sufficient hairs to cause problems in places where the caterpillars are not present, which is particularly hasardous as the cause of the health problems triggered will not be clear, delaying appropriate treatment.
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