There have been a few soldier fly sightings in our yard before, always near our compost bins. But I've never gotten a photo because the large wasp-like creatures always fly off at the slightest disturbance. Today I managed to take several pictures -- with a flash, no less -- of one that remained determinedly in place on our little rosemary shrub, without even a twitch of its antennae.
Perhaps it was a female laying eggs?
The adult female Hermetia illucens or Black Soldier Fly (BSF), likes to lay her clusters of tiny eggs near a food source for the hatched-out larvae. Although she herself does not eat and does not even possess mouth parts, she is irresistibly drawn by the availability of decomposing kitchen scraps.
Thus, the rosemary shrub near the compost corner makes an excellent site for planting the next generation. I know that our local Hermetia moms make good choices because our bins always have an ample supply of larvae feeding on the freshest, juiciest layer of new compost material -- their preferred diet.
After first discovering these fascinating creatures, I have found myself irresistibly drawn to reading articles with titles like "The Bioconversion of Putrescent Waste" and watching videos on YouTube of proud gardeners showing off piles of garbage seething with fat Hermetia grubs. (It's amazing what an innocent hankering for tasty vegetables and beautiful flowers can lead to.)
The adult flies live only about a week, just long enough to reproduce. They are quiet, elusive, do not feed on anything and do not carry disease. They are quite common nearly everywhere, like the housefly; but most people are not aware of their existence.
Just start a compost bin that meets their standards, though, and see what happens. You will discover the grubs and be horrified. Then, as you learn more, you will become profoundly grateful for a free composting service rendered by Mother Nature. During their one to three month life span the grubs consume quantities of fresh waste. They work so fast that bacteria don't have a chance to make everything smelly and other types of flies are not attracted. They quickly establish what the experts call "niche dominance" and discourage the presence of fruit flies, blow flies, houseflies, and ants. Last but not least, or even last, the residue they leave behind when they crawl away to pupate is just right for redworms, who carry the breakdown process into the next stage of creating rich soil for your garden.
So if you see a shy BSF in your yard, treat it with all due respect.
