Those little buggers shut one of my grows down. They are death on seedling roots. The larvae seem to be able to smell roots and go get em. I found a bunch of larvae literally crowded around a seedling's roots two days after I checked it and found none. All my seedlings were having trouble, so I gave up and consigned the entire grow to the outdoor compost pile. Outdoor compost was the source of my problem, it will never come into an indoor grow again.