Can I guarantee that you won’t get sick from contact with black soldier flies?
There is no species of animal on Earth that could live up to that guarantee, but researchers agree that black soldier flies (Hermetia illucens) are not disease carrying pests like common filth flies.
Black soldier flies are different
I can understand people’s revulsion at the thought of flies in general. The common house fly is associated with 277 disease organisms. On the other hand, BSF have been the subject of many scientific studies and they are not known to be transmitters of disease-causing pathogens. I’ve read dozens of articles about using the larvae to process manure and about feeding them to animals and I’ve never come across any warnings about handling BSF. It’s easier to find information about humans transmitting pathogens than about BSF doing so. You can, however, find some nice photos of researchers holding big handfuls of BSF grubs and smiling broadly (the researchers that is). There are several aspects of the BSF life cycle that result in their non-pest status.
All flies emerge relatively clean
The process of pupation results in all flies emerging relatively free of pathogens. It’s the lifestyle of the adult flies after that point that makes the difference.
BSF adults (winged stage) only live for a few days as opposed to 30 or more days for house flies. Because of their short lifespan adult BSF don’t need to eat and in fact don’t even have working mouth parts. For that reason they rarely enter human habitats and they don’t compete with humans for food. House flies must eat so they cycle back and forth between waste material and our food. It’s that cycle that results in the transfer of pathogens and it’s the absence of that behavior that keeps BSF relatively clean.
After emerging, the adult BSF mate and the female flies away in search of a suitable food source to lay her eggs near. The female’s preferred site for depositing her eggs is close to, but not on the food source. Eggs laid on the food source will have a high chance of being inadvertently consumed by already feeding larvae. This is another characteristic that contributes to the BSF status as a non-pest species.
Unlike many other flies, BSF adults do not go into houses, they do not have functional mouth parts, they do not eat waste, they do not come into contact with waste, they do not regurgitate on human food, and consequently, they are not associated in any way with the transmission of disease. They do not bite, bother or pester humans in any way. – Dr. Paul Olivier
The amazing digestive system of BSF larvae
In contrast to spreading disease there is evidence that the presence of BSF larvae can reduce pathogens in waste material.
Bacteriological interactions associated with manure digestion by maggots are favorable. Maggots are competitors with bacteria for nutrients and often reduce bacterial numbers greatly, or eliminated them altogether (Beard and Sands, 1973; Sherman, 2000). Maggots may consume and digest microorganisms, and produce antibacterial and/or fungicidal compounds (Landi, 1960; Hoffmann and Hetru, 1992; Levashina et al., 1995 and Landon et al., 1997). As maggots reduce pathogens in manure they may make it safer for organic vegetable production.
From the same article:
Flies that have been used experimentally to process manure include house flies (Musca domestica), face flies (Musca autumnalis), blow flies (usually Sarcophaga sp.) and the black soldier fly (Hermetia illucens). Except for the black soldier fly (Furman et al. 1959), all of these are considered pests as adults due to their disease vector potential, behavior and preferred habitats.
Preliminary studies with black soldier fly larvae indicated a reduction of pathogens in an artificial medium or manure innoculated with larvae. Numerous studies using dried, rendered and fresh maggots as animal feed have revealed no health problems resulting from this practice. Preliminary bacterial culturing of self-collected soldier fly prepupae from a recent swine trial revealed no pathogens
BSF grubs lessen or eliminate the breeding of pest flies
When a food source has an established colony of BSF larvae other species of flies are rare or even absent. The larvae produce an info-chemical that alerts other flies to the fact that the source of food is already being dominated by BSF larvae.
Common sense about working with black soldier fly larvae
I’m not suggesting that black soldier flies or their larvae are perfectly sterile. You and I are not perfectly sterile. Pathogens are everywhere and it is common sense to wash your hands after working with BSF, just as you would after petting a dog or shopping at the grocery store.
Stumble upon it!
Hi Kristi,
I’m building a v2.1 unit as I type. I’m taking more detailed photos than before and I’ll post a parts list very soon.
I have adult black soldier flies in my finished basement. Is this a problem? Do they eat wood timbers or wood foundations? What is their food source and how would I identify it? Even if they are not a problem, I would like to get rid of them – how can I do this?
Thanks
Hi Margaret,
First, no, BSF adults cannot harm your house or you. BSF adults (winged stage) do not eat as their only purpose in the few days they live as adults is reproduction. It’s very unlikely that the BSF are entering your house as adults; it’s much more likely they’re crawling in as larvae and then pupating. You need to find out how the larvae are entering your basement. The following link is a reply I gave someone else with BSF in a basement. The details might be different for you but the answer may be helpful anyway: http://blacksoldierflyblog.com/2008/06/13/bsf-not-vectors-human-pathogens/comment-page-1/#comment-971
I keep my bin so close and, since I am not feeding fish with them ATT they just wander off from their food source, sometimes into my house, to pupate. Notably when it’s rainy At that time, even tho the larve still have mouths, they are no longer eating any more.
Okay, tell me how BSF’s end up in my toilet. I have an enclosed septic system… only recently these ‘flies’ have become a problem. and only recently have we started serious composting. The compost bin is 150 ft from the house. there are no apparent leaks in the system. We are not bothered by an abundance of flies in the air. Help me to understand so I can eliminate an embarrassment when company comes. thank you.
Hi Frank,
Maybe it’s best if we start at the point where BSF females lay their eggs. Your septic system has drains and vents and the BSF must be coming from one of those sources. The vents might be a good candidate because they supply an easy entry point. If you want to investigate that possibility I recommend placing strips of corrugated cardboard or plastic around the vent outlet. The voids in the corrugated material are attractive egg laying sites for BSF, and it is easy to see when eggs have been deposited. In the past I’ve answered this question only based on the idea that the larvae must be from eggs laid near a hole in the tank or drain pipes, but I think the vents represent a higher probability.
These BSF got into our commercial composting toilet and we had the hardest time figuring out what the heck they were. This article was very helpful. So — they DO get into houses. But it wasn’t a big deal. They are probably actually quite helpful in processing the material. Just disconcerting when something comes buzzing up against you when you are doing your business… We do cold composting inside with our toilet (we are off the grid so can’t have a “heater” in the toilet. and have hot composting outside in a compost pile where we mix other stuff in. Their larvae are present there in abundance but I didn’t know what they were before. I’m glad to know.
Hi Susan,
What I and others promote is the idea that BSF adults don’t normally enter houses, but most houses don’t contain manure. I assume that the composting manure in your toilet does not have a strong odor, but rest assured, BSF females are experts at locating manure and rotting food, even if the scent isn’t noticeable to humans. Your attitude about the BSF is refreshing and I hope you can find a way to deal with them that makes everyone comfortable. Thanks for sharing.
Yep — We have to have a pipe vent that goes out onto the roof. It is not electric, but is driven by the updraft of the air coming off the material in the toilet. The only thing electric are two small DC fans which do keep the smell away from us and also help dry the material somewhat so that it composts in a mostly aerobic environment. I’m sure that the flies came through the roof vent, where the smell is sure to attract them. We could probably put a screen or something in the vent, but I’m not sure we want to do anything to prevent them. They are much more pleasant than many other insects that could get in there and they are very helpful. We have a hinged screen in the bathroom window, so it’s easy to let them out and they are, indeed, beautiful as you say.
Susan,
It’s nice that you and your family is able to appreciate the BSF. I’m curious about the effect of the larvae on the compost. If you live in Ohio as your email address indicates, I would expect that the adult BSF are finished for this year, but the larvae may survive through the winter in your compost. It would be great if you can provide occasional updates on your observations.
Thanks!
I am back. The last two years we had abundant soldier fly larvae. This year almost nothing and thus our compost isn’t nearly as good. What is the best way to bring them back again? Atlanta, GA
hi, im from venezuela, last month a friend went to USA and brought me 25 bsf larvae, im pretty sure that we dont have bsf in venezuela or at least not in my city, so im trying to breed them in order to build a bio composer and feed my reptiles. im afraid that im running out of time by waiting for the bsf to mate, i keep the flies in a glass terrarium of 80x50x70 cm with some plants and the compost inside a carton box with some holes so the flies cans get inside it, the temperature is on 86 and the humility is on 90% , but they dont even try to made. what can i do? is there any advise for activating their mating sense?. i have only 12 flies left. i need help
P.S: excuse my bad english
angel you should have a look at the following blog:
http://eatingoffthefoodgrid.blogspot.com/2010/09/black-soldier-fly-update.html
She uses a glass terrarium with a netting enclosure above to allow the flies to mate in flight.
Hi! I’m a vermicomposting addict, but I must say this is very intriguing to me.
I’m from Manila and I can’t seem to find suppliers for BSF.
Any ideas?
Thanks!
Great anecdote. Makes me want to find BSFs in my compost bins too!