It is at this time of year that the caterpillars head to woodland floors in search of a place to pupate and it is when you will see the characteristic long lines as they follow each other nose to tail.
And while that is a view of nature to behold, the Pine processionary caterpillar has a horrible 'feature', the small hairs on its back are poisonous and can be a terrible irritant if touched.
But cats and dogs are particularly at risk as the fine hairs can become embedded in the mouth, or stomach, and if not spotted quickly and dealt with by a vet, can prove fatal.
Beyond keeping your pets close to heel, there is little you can do to keep the caterpillars at bay. Professionals will use blow torch apparatus to burn the insects, but the trees in a small area will play host to hundreds of nests.
So just keep an eye out between now and May for the Pine processionary caterpillar, stay clear of pine trees if you are worried, and let the beasties progress on their way.