bluergh

The children and I have been tidying up the garden and starting to plant our vegetables ready for the summer crop. This afternoon I was potting up lots of seperate pots from the sacks of compost that we grew our potatoes in last year. Due to having cats the first job is inevitable and then I was moving the compost. Then I dug up 7!!!! of these. Apart from one small one they are all this size, huge and disgusting. I have looked them up on t'net and it looks like they are cockchafer grubs otherwise known as the mayfly. Thing is it says it takes 3-5 years for them to reach this size and I bought the compost last year so they must have been in there already!!! Who knows where they came from?? I have transfered them all into another tub and buried them again as I really don't know what to do with them. Are they pests?