Black soldier flies are slender flies about 18 mm long and 5 wide with a dark black body and transparent wings, usually folded together on their backs. The flies are fairly slow moving, often not even trying to escape. They mimic the appearance of wasps to scare off predators but can’t sting or bite.
The larvae of Black soldier flies feed on decomposing material and are often found in compost bins. The adult flies don’t eat at all, they don’t even have a functioning mouth. They only life a short life to mate and reproduce.
Black soldier flies larvae are very welcome in our compost bins. They deter blow- and houseflies from our compost and they are very efficient in breaking down food waste into compost. They should be kept out of our worm-farms though since they produce a warmer and more acidic environment than the worms in our farms prefer.