This story originally appeared in the San Francisco Chronicle
SANTA CRUZ, Ca. - (July 2008) - I’ve been composting my kitchen waste for 20 years, and there’s not much in the way of rotting food that can gross me out anymore. But then, last summer, the maggots appeared.
For years we had an open-air compost pile that we’d manage by layering food scraps with leaves and soil, then turning over periodically. We saw bugs occasionally, but the turning kept them from getting too comfortable.
Then the city sold us a set of plastic, rodent-proof compost bins, which tossed a wrench into the works. The shape of the bins prevented turning of the compost, which then took ages to decompose, leaving layers of anaerobic gunk that stank to high heaven when you shoveled it out. The new bins kept the rodents out, but they allowed other creatures to move right in.
One afternoon, during a mid-summer heat wave, I went to toss a bucket of food scraps into the bin when something in there shifted. The surface of the pile was gently undulating -- or was it a heat-generated mirage? A carrot top appeared to be waving at me, a scrap of bread bobbed up and down. I bent in for a close look, and promptly regretted it.
The bin was boiling with brown and beige maggots, big leathery fellows three-quarters of an inch long, and nearly a quarter-inch wide.
My scalp began to tingle, and I frantically checked my bare legs for creepy crawlies. I hurled the scraps into the bin and fled.
I didn’t know what to do about this infestation so, once my alarm subsided, I decided not to do anything. Besides, I was curious to see what would hatch out. If the result was unpleasant, I figured, those rodent-proof bins were history.
GOING BUGGY
Over a period of weeks I noticed interesting things about my new tenants. For one thing, they ate like crazy. If you tossed it in, it vanished within hours. And the compost no longer stank, it now had the mild odor of damp straw.
The maggots were very responsive – they pounced on new food, and retreated from direct sunlight. You could hear them. The mass of moving larvae made a wet rustling sound, exactly like falling rain.
Yet nothing appeared to be hatching from the larvae, which had increased in number to approximately a billion. Oddly, the other compost flies had also vanished.
Perhaps I’ve been working at home too long, but I became rather fond of my maggots. I took frequent breaks from the computer to watch them at work, and fretted about them when we went on vacation. I’d say things like “Come and get it!” when I brought out a new load of scraps.
I worried that the neighbors would find out.
Vegetable peels, plate scrapings, the newspapers that lined the compost bucket – about five gallons of waste per week – all were gobbled up so fast that the compost pile began to recede. I tossed in squishy plums and wormy apples from our trees, five or ten gallons at a time. They’d be gone by morning.
BAD GARDENER
There are things you’re not supposed to put in your compost pile, things like cheese and meat, and oily cooked food. But I wondered what the maggots would do, so I cleaned out the refrigerator one day, and brought a fatty, protein-laden banquet to the compost bin.
My bucket was brimming with forbidden things; hairy sour cream, chicken parts, a wad of bacon-grease-soaked newspapers. I felt like a bad, bad gardener, but I tossed it in anyway.
An hour later I peeked in, and no doubt about it, there was a party going on. The maggots were at a rolling boil, thrashing about in a feeding frenzy. Most arresting was the fate of a fist-sized ball of formerly fresh mozzarella. The maggots had tunneled into the cheese, which held its shape but quivered violently. Within another half-hour it was gone.
I took my husband out to show him the action, and sheepishly revealed my experiment. He gazed into the mosh pit, raised an eyebrow and said, “Don’t fall in!”
I laughed, but decided it was time to find out if our bugs had any dodgy habits that the health department might be interested in.
BACKGROUND CHECK
A little Internet surfing answered my questions, and more. Our maggots were the larvae of black soldier flies, (Hermetia illuscens), often referred to as BSF, a native fly whose amazing environmental usefulness is just now being explored.
 While BSF have probably always lurked around my compost pile, they didn’t thrive in large numbers until the rodent-proof bins prevented me from turning the pile. In addition, mice, rats, raccoons and birds all consider BSF larvae quite delicious, and had probably picked off the ones that managed to hatch.
When kept warm and protected, BSF larvae are probably nature’s best composters. They can consume the manure from factory farms, food scraps from homes and restaurants – almost any type of wet and icky organic waste.
Despite their voraciousness, the worst thing about falling into a vat of maggots would be the resulting nightmares. BSF can somehow tell the difference between living and non-living tissue, and eat only the dead stuff.
Because they eat so quickly, microbes can’t begin to break down the waste and produce smelly methane gas, one reason why my compost stopped stinking. In addition, the larvae secrete chemicals that kill bacteria – converting even pig poop into a safe, non-smelly soil amendment, according to one study.
The lack of adult flies was due to BSF’s solitary nature. Adult flies live less than a week and don’t eat. The mature larvae crawl away from the compost pile to pupate, and the flies quickly mate, lay eggs and expire.
Our other compost-loving flies had vanished because the BSF out-compete them, and prevent them from breeding. And unlike other flies, BSF are not attracted to human homes or food, and do not spread disease.
The down side to BSF larvae is that they become sluggish as the temperature drops below 68 degrees Fahrenheit. A hard freeze will kill them, but in moderate climates they survive by burrowing deep into organic matter and going dormant until the weather warms. Commercial bug farmers (yes, there’s a market), have figured out how to keep their grubs warm and happy all winter long, but my free-range population dwindled away by Thanksgiving.
BUGS BY MAIL
I could have waited for them to re-appear as spring arrived, but lacked the patience. Thank heavens for mail order!
I contacted the Phoenix Worm Store in
Tifton,
Georgia, and within two days received 600 small-size BSF larvae, hungry and ready to go. The Phoenix Worm Store sells mostly to reptile owners, because BSF larvae are packed with calcium and their wriggling stimulates the reptilian appetite.
Phoenix Worm founder Craig Sheppard, a retired entomologist and a world expert on BSF, raises his larvae on a sterile grain-based diet. But his pampered maggots instantly burrowed into my icky compost, ate like champs and began to pupate within three weeks. I’m now waiting for the next generation to turn my pile back into a teeming maggot buffet. My refrigerator is due for another cleaning.
This article originally appeared July 26, 2008, in the San Francisco Chronicle
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