The processionary caterpillar
If you look in the pine trees at this time of year, you are sure to see a weblike covered cocoon, in it are hatching and growing processionary caterpillars, Not only do they devastate thousands of hectares of pine woodland every year. They cause bad skin irritation and can cause blindness, sometimes permanently, if handled. Dogs and cats are inquisitive and can suffer very painful death if they sniff or lick them.
If you have them in trees on your land the best thing is to try and set fire to the nests or cut out the branch and burn it.