I found loads ofthe grubs of these when pulling out grasses by the roots in a patch that hadnt been touched for years. Apparently they can decimate lawns and eat some plant roots. So - it depends where you find them as to whether theyre a problem or not. They are fascinating to dig up and have a good look at. Couple of inches long at full size some of them. I imagine great bird food , so we need some around. The conventional chemical control, can harm birds and other creatures - if you need to get rid of them , try biological warfare!
http://www.amazon.co.uk/LEATHERJACKET-KI...words=nematodes