The Deadly Caterpillars

While we were driving through the forests of the Auvergne on the way to Céreste in December, we noticed that many of the pine trees were festooned with large silken balls.  In many places, there were so many that the trees looked positively festive, as if Mother Nature herself had decided to put Christmas decorations up.

We had no idea what they were, but assumed they were the nest of a spider or some sort of insect.

We've seen plenty more of them since we arrived in Céreste - the above photo was taken about two miles from our house.  Eventually we remembered to ask someone what they were, and we were shocked to discover that something so decorative is in fact something quite dangerous.

They are the nest of the caterpillars of the Pine Processionary Moth, a nondescript brown moth which a pest which is slowly invading Europe from South to North.  Each nest can contain a couple of hundred caterpillars.  They are nocturnal, and emerge from the coccoon at night to munch on their tree host.  They can do quite a lot of damage to the trees, but that's not the bad part!

When the caterpillars leave the nest, searching for soft soil in which they can bury themselves to pupate, they travel in a line, literally nose-to-tail - hence the name, "Processionary."  They are slightly hairy, which is essential for their "processions" as each caterpillar keeps in touch with the one in front by means of their bristly hairs, in addition to following the silken path laid down by the ones in front.

This all sounds fine, right?  Why are they dangerous?  Well, their bristles are coated with a highly irritant substance which causes a rash (urticaria) at least, and a severe allergic reaction at worst, causing anaphylactic shock in some people and animals.  Small children and small pets are at the greatest risk - you can just imagine a toddler finding the chain pictured above and wanting to investigate closer.

Friends who live down here have a dog which has half a tongue, as a result of licking one of these caterpillars - her tongue swelled up, her whole mouth was irritated and she had to have half her tongue removed in order to survive.

Not only does touching them cause damage - if they feel threatened, they can also shoot out hairs as part of their defensive mechanism, causing the same skin irritations.

People have been hoping that the severe cold spell here in early February will have killed off the caterpillars in the region, but unfortunately, this is not the case.  We came across the "procession" pictured here recently, proof that these pests have survived the coldest winter in 27 years.

The head of the procession - it seems a bit jumbled and confused

The tail of the procession

We'll keep the dogs leashed any time we're in pine forests from now on, and we'll probably keep out of the pine forests as much as possible as well.

There was a study done by the French entomologist, Jean-Henri Fabre.  He arranged a number of caterpillars in a circle, with food just outside of the circle.  They marched in a circle for a whole week!  If you're interested, the relevant chapter is here : http://www.efabre.net/chapter-iii-the-pine-processionary-the-procession

If they weren't so dangerous, they'd make a great cheap substitute for a toy train set!