Walk on the Wild Side- The Pine Processionary Moth Caterpillar.

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A Pine Processionary Moth Caterpillar Group.

A Pine Processionary Moth Caterpillar Group

When walking in the hills here in the South West of France don’t be surprised to see a number of white woven silk-like structures in the branches of pine trees hanging like strange Christmas decorations. These are in fact the nests, termed as ‘tents’, created by the larvae of the pine processionary (Thaumetopoea pityocampa) moth.

A Pine Processionary Moth Tent.

A Pine Processionary Moth Tent.

Although they are intriguing structures the larvae which are contained within are considered quite a forest pest. Natural predators include birds like the common cuckoo (Cumulus canorus) , European nightjar (Caprimulgus europaeus), hoopoe (Upupa epops), crested tit (Lophophanes cristatus), coal tit (Periparus after) and great tit (Parus major) (which I’ve regularly observed pecking at the nests here in the Aude). If, however, populations grow to large numbers they can severely defoliate the trees in which they inhabit thus weakening their hosts making them more susceptible to pests, diseases or extreme weather conditions. Their popularity is not helped any further by the fact that each one is covered with thousands of hairs containing a protein called thaumetopoein which can irritate the skin and cause allergic reactions. A great defence mechanism to have evolved but unappreciated by us -especially when found in urban or built up areas.

Much of the sensitivity around the pine processionary moth also seems to be due to their current direction of travel. Although the caterpillars can be described as being nomadic (locally at least) their range was, until fairly recently, isolated to the Mediterranean region, southern Europe, North Africa, Central Asia and the Middle East. This however is now changing. Here in France, possibly due to a cocktail of climate change creating warmer winters and unintentional human assistance, the pine processionary has moved northward and has spread as far as Normandy and Brittany.

 Pine Processionary Moth Caterpillars forming a line.

Pine Processionary Moth Caterpillars forming a line.

Pine Processionary Moth Caterpillars forming a line across a path.

Pine Processionary Moth Caterpillars forming a line across a path.

They are, however, fascinating creatures. We came across two processions of the caterpillars here in the Languedoc quite by accident one day towards the end of February 2016. After overwintering the groups make their way down from their host trees forming their trademark processions on the ground before finding places to pupate in the soil and on this day (one of first decently warm days of the year) we spotted a bundle of the hairy orange-brown and grey banded caterpillars in the middle of a public footpath which hugged the River Aude. Although many of them were still in a tight group it was amazing to watch how they slowly organised themselves to form one long continuous line of around 4 metres to form a kind of spontaneous Andy Goldsworthy natural art installation. How they decide the hierarchy of which caterpillar goes where one can only guess but it was fascinating to watch each individual vying for position to join the line which cut across the path. A video I took of what we saw can be seen here:

If you are lucky enough to come across these amazing processions in Continental Europe take time to watch but remember to keep at a safe distance and observe them with care!  If you do see any signs of the pine processionary moth in the UK then contact the Forestry Commission here.

Further information about the pine processionary moth can be found at :

http://www.forestry.gov.uk/pineprocessionarymoth

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