March fly larva
Some people have been concerned about large numbers of unusual looking 'worms' they have discovered under leaves or compost piles in their yard. The insects in question are march fly larvae, belonging to the family Bibionidae. They are generally dark-colored and grow to be about 1 inch long. They have a conspicuous head but lack legs. They also possess short spine-like setae (hair-like structures) over much of their body.
March fly larvae feed on decaying organic debris and often are quite numerous. They are typically found in the soil under leaves, manure, and other areas of high organic matter. They also can be found in grassy pastures and meadows and on forest floors. While there are also records of march fly larvae feeding on the roots of grass, that is rarely, if ever, seen in Minnesota. It isn't necessary to manage march fly numbers in your garden. Just ignore them.
Published in Yard & Garden Line News, May 15, 2002