Pine processionary moth and hairy caterpillars in France

With the aid principally of social media in all its aspects the Pine processionary moth increasingly strikes fear into the population with all the stories about how dangerous they can be.

There is certainly no denying their harmful nature should someone or their pet animal come into close physical contact with them or breathe in their harmful hairs but we mustn’t let this lead us into a panic that results in the destruction of our other native hairy or web forming caterpillars that need all the protection that they can get.

The first thing to understand is that Pine processionary moth nests are always in Pine trees and only rarely in Fir trees. A caterpillar web anywhere else is a different type of caterpillar.

Secondly, when on the ground they will invariably be found in the classic processions “nose to tail” and only very rarely as individuals should they have been blown from the trees by storms.

Thirdly, they will only be found on the ground when Pine or Fir trees are in very close proximity.

Moving on to a few other web forming species with one that always causes undue worry and that is the Spindle Ermine Moth that form large webs on Spindle trees often completely covering them and stripping all the leaves. This usually occurs in early May when the first leaves are produced and despite it looking like a disaster zone more leaves are produced when the caterpillars descend to pupate and the tree busts back into life.

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Spindle Ermine Moth

Another species that was once very common but now in decline principally due to hedgerow removal and poor management is the Small Eggar Moth. The caterpillars form dense webs on Hawthorn and Blackthorn. Again the host plant recovers once the caterpillars have descended to pupate.

Small Eggar Moth

Various species of Ermine moth can be found on apple trees and these again are harmless to the overall health of the tree and humans although they may cause damage to fruits should the web engulf them.

Ermine moth species on Quince tree

There are of course many hairy caterpillars that don’t form nesting webs and all hairy caterpillars can cause skin irritation and allergic reactions but this would normally only be if they came in contact with sensitive areas of our skin or if someone was unusually sensitive. As children we used to have great fun putting them down each others shirts to cause itching. However that said they will have no effect on the harder surfaces of our skin such as our fingers and the palms of our hands.

I’ll provide a small selection here of some of the more common species that people are likely to come across and I can't emphasise enough the need to care for all our native species that are struggling so much. Without caterpillars and moths a huge number of other species will starve without enough to eat. One Blue Tit chick alone can eat up to 100 caterpillars a day.