‘Phoenix worms’ rise up - and close the loops
The more I read about block soldier flies (abbreviated BSF’s, apparently) the more I appreciate what they are doing to my compost. It wasn’t always like that. A few months ago I turned the pile and saw thousands of maggots writhing about. “Oh great! I’m producing flies by the thousands!” I thought. Now I know they aren’t housefly larvae, but the beneficial BSF’s.
How beneficial?
For one thing adult BSF’s pollinate flowers, and do not eat your food like annoying houseflies. In fact, they tend to stay away from homes. After aerial mating the females deposit egg masses (~500 eggs) adjacent to rotting organic matter.
The real magic is caused by the gross maggoty larvae, which are also romantically dubbed ‘phoenix worms’. Like the phoenix, from the waste comes a bundle of energy. Unlike the phoenix, they don’t fly - in fact they just wriggle and eat like crazy, oft times reaching over an inch in length. The BSF larvae (BSFL) quickly, voraciously, consume fresh organic matter, so rapidly that they compete with decomposing bacteria and thus PREVENT typical odors of rotting food/manure. I begun adding spent barley and wheat grains from my homebrews, even beans that have gone bad, and found that, thanks to BSF, these highly nutritious (i.e. smelly) grains and legumes did not cause a bad stench like they normally would.
Ridding of nasty smells is pleasing but not necessarily valuable - what about the nutritive value of compost decomposed by BSFL, as well as the fattened-up BSFL themselves? The larvae appear to increase the bacterial activity of the soil, speeding up the digestion of cellulose. Composting earthworms appear to thrive on residue produced by BSFL. This residue is likely less stressful for the worms than fresh organic matter. The residue is also safer for humans - BSFL consistently reduce potentially pathogenic E. coli and Salmonella enterica in chicken manure (1). Furthermore BSFL are even known to prevent houseflies from depositing their eggs (2)!
Upwards of 40% of nitrogen is lost from the organic matter and converted to the flies themselves (3). The larvae are highly nutritious to animals. In fact, they contain 42% protein and 35% fat and have been fed to fish in aquaculture systems with some success (4), and may even be fed back to livestock such as chickens and pigs. Their oils have even been effectively extracted and used as bio-diesel (3).
(1) http://landbouwwagennld.library.ingentaconnect.com.ezproxy.library.wur.nl/content/iafp/jfp/2004/00000067/00000004/art00009
(2) http://www.springerlink.com/content/gwqgn0736t12v50h/
(3) http://www.cals.ncsu.edu/waste_mgt/smithfield_projects/phase2report05/cd,web%20files/A2.pdf
(4) http://www.sciencedirect.com.ezproxy.library.wur.nl/science/article/pii/S0956053X11000158
