Pine Processionary pests

Every year the Pine Processionaries come out of their nests high up in the local pine trees in April time and march along... Im not sure where to though.  Ive read that they burrow just below ground to make a cocoon and then emerge at the end of summer as moths. This 'procession' gives these little hairy caterpillars their name as they go along tip to tail, all joined together.

I'd not heard of these types of caterpillars before and thought the whole thing was really cute until people told me that they are one of the most destructive species to pine and cedar trees in the area especially if mild winters assist their development.  They are responsible for most of the defoliation in Southern Europe though as they come out at night and feed on the pine needles.  Also, their little hairs also cause harmful reactions to humans and animals.  They tell me that if dogs and cats get too close to them and come into contact with their hairs the allergic reaction can kill them!  So be careful!

In the autumn, people with pine trees in their gardens get them sprayed with insecticides to stop them nesting in their first and second stages of growth.  You can see them on lots of rural pathways in the spring and I know that when people come across them they try to get rid of them in a safe way.  If you do see them over here, just do not pick them up or handle them.

Have you seen them before?