Magic of the recycle bin and an edamame surprise: Soldier flies, Stratiomyidae
Black soldier flies have a wasp-like appearance but pose no threat to humans or pets.
Lurking in a corner of the recycle bin, a fishing spider awaits its next victim. Will it be a maggot, fly, or another member of the food web within the compost bin?
More than a decade ago, I purchased a modest black plastic bin to recycle vegetable waste. This mysterious contraption, seemingly nothing more than an empty box, has somehow magically converted thousands of pounds of plant material into less than 150 pounds of dark granules that look a lot like soil. Yesterday as I added yet another load of watermelon rinds, banana peels, egg shells and assorted other vegetables, I took a deeper dive into the workings of this marvelous device and was greeted by legions of fly larvae. That’s right, the real workhorses of my recycling wonder are maggots, industrious geniuses driven to convert plant protein into animal protein. In so doing, some of these maggoty morsels of protein become food for predators like spiders and beetles that lurk in the corners and slither through the mire of the bin. When they pupate and then emerge as flies, out of the bin they go to become food for birds, dragonflies, and other carnivores higher up the food web. Plant becomes insect, and insect becomes food for other animals.
One of the key players in this transfer of energy and biomass is the black soldier fly, Hermetia illucens. Due to their high metabolic efficiency in converting decaying organic matter into fly protein, larvae of the black soldier fly have been commercialized in some parts of the world to turn compost and manure into feed for animals like chickens, pigs, and fish. An added bonus of their recycling acumen has led farmers to consider them as a partial solution to managing manure generated by hogs and chickens. One report has it that 45,000 black soldier fly larvae can consume more than 50 pounds of manure in two weeks. Now that’s a lot of repurposing. In a strange game of turnabout, after black soldier fly larvae eat manure, their frass (excrement) can also be used as soil amendment to improve crop yield.
Magic happens in this plain-looking compost bin. Beneath a banana peel and throughout the bin, legions of fly larvae convert plant protein into animal protein. Foremost among the magicians are soldier fly maggots, which cruise decaying vegetables and fruit. A female black soldier fly searches the inside of the bin and finds just the right cranny in which to deposit her eggs.
What a surprise, a soldier fly larva in my edamame.
Years ago, I had another interesting encounter with soldier fly larvae. Edamame is one of my favorite foods, loaded with protein, fiber, and important minerals like calcium, iron, zinc, and potassium, yet low in fat and sugar. Who wouldn’t want to eat these tasty nuggets from the soybean plant? The great thing about edamame is the fact that it now comes in a microwavable pouch. You just toss it in the microwave and in four minutes these nutritious morsels are ready to eat. After a hard day of chasing bugs, this quick and easy meal is a real treat. One evening after steaming shelled edamame and dumping them onto my plate, I was amazed to see a large and juicy soldier fly larva ensconced amongst the beans. This was no tiny maggot, no sir, this one was a last instar larva, ready to pupate any day. Alas, its life was cut short and it somehow wound up in a steamable edamame pouch. Now, I have eaten many an insect in my day, some inadvertently in a squidgy tomato infested with tiny fruit fly larvae or as microscopic moth eggs in my cereal. On several occasions I have dined on cicadas or meal worms to promote the importance of entomophagy as a partial solution to the global protein shortage. Insects really are a wonderful protein supplement and in some parts of the planet, they are on the menu daily. However, on this occasion, I just couldn’t bring myself to eat this extra morsel of protein. Here’s why. The interesting thing about soldier fly maggots is where they live. Some live the life aquatic and feed on algae, others feed on decaying vegetation and organic matter, and still others develop in dung. Not knowing exactly where this larva dined before winding up with my edamame hastened my decision to eschew this petite surprise. Who would have guessed that maggots in a compost bin or in a serving of edamame would be so interesting?
Acknowledgements
The interesting article, “Using the Black Soldier Fly, Hermetia illucens, as a value-added tool for the management of swine manure” by Newton L, Sheppard C, Watson DW, Burtle G, and Dove, R, was used to prepare this episode. To learn more about the black soldier fly, please visit the following website: http://edis.ifas.ufl.edu/pdffiles/IN/IN83000.pdf
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