Compost Critters

My editor was turning our compost in the backyard bin when she discovered it was full of squiggly creatures.  She identified them as black fly larvae, Hermetia illucens.  While this was a new species to us, it is apparently a very common finding in compost piles that aren't turned frequently.  Not only are they our friends, in many countries they are an industry.

Mating occurs two days after the flies emerge.  The males will have a lekking site where they gather similar to prairie chickens and may attack competing males.  They then fly up to grasp a passing female for copulation.

Home "sweet" home

"The female black soldier fly deposits a mass of about 500 eggs in cracks and crevices near or in decaying matter such as dung, carrion, garbage, and other organic waste. The eggs hatch into larvae in about four days. Each oval shaped egg is about 1 mm in length." UFL Entomology

Final instar 22 mm - head on the left and "you know what" emerging on the right.

Small head with chewing mouthparts

The larva is a pale off white color with a small projecting head equipped with efficient chewing mouth parts.  The larva will gorge constantly over two weeks, splitting out of its skin six times.  The final instar is up to an inch long. When ready to pupate, it will climb out of the moist pile of  manure or decaying matter to find a dry surface.  There the skin (exoskeleton) darkens and a pupa develops within.  Inside it transforms into the fly over two weeks before emerging to repeat the cycle.

Pupa case

Another happy customer!

A very low tech operation can raise livestock food as well as convert animal and vegetation waste into a usable resource.  This 4 minute video shows the full process as done in Malaysia, producing both compost and livestock food seen at the right. One ton of organic waste is converted into over 400 pounds of compost plus 400 pounds of larvae for poultry.  Now that is a lot of chicken food!


This University of Florida Entomology website has a very thorough description of the fly and its life cycle as well as photos of the stages.

Update 5-26-2020
This Black Soldier Fly was on a leaf next to the compost bucket.  Its our baby!