While we were out we saw some evidence of nests (see photo - didn't want to get too close) belonging to Processionary caterpillars which are a bit of a health hazard according to the local free English newspaper. These caterpillars feed on pine trees and build nests that look like cobwebs - see picture. They have bristles which can be an irritant and in worse cases cause anaphylactic shock in some people and animals if they touch or injest them. Caterpillars congregate in the nests and as they moult and lose their bristles they can get into the air and blow around. Around Spring time the caterpillars take to walking end to end in long processions sometimes several metres long and then a curious child or animal might touch them with unpleasant results.