Soldier Fly Larvea can be a rather freaky find in your outdoor or indoor worm compost bin. You can often hear them "chew" on your compost! They are also called a Window Fly. The following is an excerpt from the Oregon State University Garden Hints website and the quotes are from Cindy Wise, “Soldier fly larvae are voracious consumers of nitrogen-dominant decaying materials, such as kitchen food scraps and manures.‘Don’t worry, soldier flies don’t usually invade houses, unless your compost pile is close to your house,’ said Wise. ‘They almost exclusively populate compost bins or sheet mulch compost piles and manure piles,’ she said. ‘In the southern United States they are being utilized to reduce hog manure, as they can consume up to 30 tons of hog manure in two days.’ Soldier fly females lay eggs on the surface of nitrogen-rich material that is exposed. So, if you want to avoid having these large flies and their maggots in your compost pile, make sure you have enough leaves, dry grass, shredded paper and other organic “brown” material in the pile to cover the nitrogen food sources by at least two to four inches. Remember to bury food scraps deep down in the pile and cover them.
They often thrive in worm bins, as well as compost bins, where they may compete with the worms for food. ‘In a worm bin, bury food scraps down at least six inches for the worms and let the flies eat what is on the surface,” said Wise. “The flies don’t eat the worms or their eggs so they aren’t predators of the worms.’ The maggots are known to break down organic material in the pile so it can further decompose. And the flies inoculate the compost with beneficial bacteria from other sources."