Ralph discovered these things in our compost heap. Yikes! There were millions of them, it seemed, busily munching on a head of cabbage that had split and gone bad. We’d dealt with an earwig infestation earlier in the season. Was this a harbinger of future earwigs?
Ralph put a few in a jar and took it to the Master Gardeners at our local college. They scratched their heads and told him they’d get back to us. We got on the Net and decided that the most likely culprit was Black Soldier Flies.
A few days later a Master Gardener showed up and confirmed the diagnosis. Black Soldier Flies are beneficial. They lay their eggs in decaying material. If the heap is too moist to support earthworms, the BSF larvae take over. They eat things (like cabbage leaves) too solid for earthworms to feed on, and poop out earthworm chow. The adults are pretty unusual, too. Most flies eat by barfing stomach acid, then lapping up the resulting slime. (This is why they are disease vectors.) BSFs eliminate this problem by not having mouth parts.
You read that right. Adult BSFs have only one thing on their minds: making more BSFs. They do all their eating as maggots, and boy, do they eat! A few days after this photo was taken, Ralph emptied a vacuum cleaner bag full of dust and dog hair into the heap. The maggots (having run out of cabbage, I suppose) rose up through the heap and started eating the dog hair.
But here’s the really neat part. The Master Gardener looked at our garden and said, “I’ve been gardening for 30 years, and this is the nicest garden I’ve ever seen.”