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 larvae 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 larvae 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.
Comments 25
Very interesting article here!
I haven’t yet read the source material so will still need to look them up, but have to say the larvae look more like woodlice in your picture!
Posted 19 Jun 2008 at 9:26 pm ¶Hi Mosey, thanks for visiting! The BSF larvae do resemble woodlice in a photo, only the BSF are MUCH prettier.
Posted 20 Jun 2008 at 7:14 am ¶Howdy,
Posted 25 Jun 2008 at 2:15 pm ¶I found BSFL in my compost last year and looked them up online and the info I found on them made me happy. They are impressive little critters.
So far this year they haven’t made an appearance in my compost. I think it’s because I haven’t been stopping by the coffee shop and getting grounds like I did last year. It seems they really like that stuff.
Glad to see your blog. I think these critters are awesome.
Hi Dirk.
I’ve noticed the same thing about BSF and coffee grounds. Could they be caffeine junkies? One theory I have is that the grounds help them digest food more efficiently because of the caffeine, the texture, or both.
I’m glad you found my blog and I hope you’ll let us know if any BSF larvae show up in your compost.
Posted 25 Jun 2008 at 8:52 pm ¶BSF larva are also known as ‘Phoenix Worms’ and are excellent feed for insectivores such as Reptiles, Birds, Tropical Fish, and Sugar Gliders. They are High in calcium (about 50x +/- more then other feeder insects) and lower in fat. They also make extraordinary composter insects that can consume large quantities of food including meat and dairy before it even rots.
Posted 20 Aug 2008 at 11:22 pm ¶I’m in Maryland. Had to go to metal trash can composters, as there is a rat problem here. Noticed maggots in the compost this summer. But how do I know whether they are the disease carrying houseflies or black soldier flies? Thanks.
Posted 27 Sep 2008 at 10:27 am ¶Hi simone,
House fly maggots are smaller than that of black soldier flies. A BSF larvae can reach almost an inch in length.
You can also observe the area where the maggots are located to see what type of fly is present. If you see more than 3 or 4 house flies around the pile then the larvae are probably not BSF. If you see no, or few houseflies around the pile I would suspect you have a BSF colony because BSF larvae give off an info-chemical that repels other species of flies.
If you really want to be certain about the species the best way is to put a few maggots in a jar and see what develops. If you provide them with food, water, and air you will soon have an adult fly to identify. House flies develop much quicker than BSF so if you have them you’ll know within a few days.
Posted 27 Sep 2008 at 2:21 pm ¶Me and my daughter found tons of these bad boys when stirring the compost today, we immediately recognized them as larvae, thought fly species likely, and found our way to here from searching “big larvae in compost” then searching the genus and species viola! Not many flies found in compost have such large larvae- a handy characteristic for identification. They actually look much less dingy when you bathe one in water. less brown, more yellow. We especially like their pointy heads (my son, daughter, and I) This blog is excellent, we’re going to slap the one we bathed under the dissecting scope to get a closer look. I can email my drawings if they’re any good and you are interested. I am a lab instructor for an ecology class at the University of Oregon. Me and my children study insects for fun. Thanks for a great blog, good info can be hard to find.
Posted 29 Sep 2008 at 10:10 pm ¶Jarrett, thanks for the kind words, I’m glad you had a good experience with the BSF larvae. I was laughing at myself today because I was cleaning up on of the three larvae I’ve been photographing daily. You can see that thread here. One of them had a piece of food that didn’t wash off and I had a tissue rolled up and I was gently wiping it clean.
I would love to see the results of your examination.
Thanks!
Posted 29 Sep 2008 at 11:12 pm ¶Zoonotic Parasites?
Like many pet owners I have a pet poop problem my BSFs LUUUUUV poop and have taken over the bin I used to deposit them in. The resulting compost I have dropped on the landscaping trees and not much else because I’m conserned about the possibility of zoonotic parasites.
Has anyone studied this as a transmission vector?
Posted 09 Dec 2008 at 1:35 am ¶Hi Pego, sorry it took me so long to respond!
I don’t believe there is reason to worry about using the compost for growing vegetables. I’ll check back when I have some sources to share.
Thanks,
Jerry
Posted 15 Dec 2008 at 8:49 pm ¶I am very interested. I am ina pet service industry and find myself giving the Toxocariasis lecture to people who hqave the perfectly normal idea of walking barefoot in the grass that has had pet traffic. I would so love to see some research and show it to some of my clients and friends.
Posted 16 Dec 2008 at 2:42 am ¶oHHh… i thought they are pest.
i found many of them on my backyard just suddenly and i wonder where do they came from?
hoping for your respond!
thank you!
Posted 07 Apr 2009 at 6:42 am ¶Hi JuwANna,
Black soldier flies are native to the southeastern U.S. but they have spread around the world, mostly in the tropics and subtropics. They thrive anywhere that the climate is warm and humid. They can be cultured almost anywhere, but they would not survive in the wild unless the conditions were favorable.
Thanks for commenting!
Posted 07 Apr 2009 at 8:19 am ¶oWwwww!
Posted 08 Apr 2009 at 2:46 am ¶i’m from the philippines in mindanao
and i can’t seem to figure it out where did they came from. it just sudden that they appeared on nights. do they actually live on trees?
juwANna, the black soldier flies have most likely been present on your property for years but they went unnoticed. The adult flies only live for a few days and aren’t attracted to people. I live where the BSF originated and they are very common, but most people here could not recognize an adult BSF. Many people here have seen the larva though, because they live longer and stay in one place, assuming the food supply is consistent.
The adult flies are attracted to bushes after emerging and there they mate. After that the males are rarely seen and females seek out rotting food so they can lay their eggs by a good food source. After mating and laying eggs the short life of the BSF adult is over.
Most of the people in my area know about BSF larvae because they are excellent for fishing bait. Once people use them they tend to seek out the larvae for this reason.
Posted 08 Apr 2009 at 7:37 am ¶I’m from Davao, Philippines. I’m happy to tell you that after searching the net for BSF infos, I finally made myself a bin where we throw our kitchen wastes including pig manure and chicken dung from our nearby farm. The results are great! Not only do we reduce our garbage (only non-biodegradable materials were thrown as garbage) but we also have lots of larvae to feed our chickens and flowerhorns. The rest / part of the wastes goes to my methane digester where we use it as fuel for cooking. I am currently planning to put the BSFL poop to my nearby vermi project.. Your blog is of great help. Thanks!
Posted 22 Apr 2009 at 12:36 am ¶Hi I posted a link to your blog this week because I have discovered BSF larvae in the compost pile I happily started when I moved to Hong Kong just a few months ago. I was immeasurably relieved to find out these guys are actually good and maybe even great for my compost pile. Now if only I can convince my kids & neighbors…
Thanks loads for your great info.
Posted 23 May 2009 at 4:21 am ¶Hi Jerry, I hope I can use your blog to send a message to a countrymate regarding BSF. Really desperate to find some for our Farm, thanks!
Hi Bong (from Davao, Philippines), this is Regina. I am based in Quezon City. Can I buy a few pieces of your BSF larvae? I would like to cultivate BSF for our farm to get rid of the houseflies. Please email jemerc(at)gmail.com if you are ok to sell. Thanks.
Posted 01 Jun 2009 at 8:27 am ¶Hi, we have a worm factory that we keep in our basement and I found that we have many of these BSF’s now, Is there a way to get rid of them? How could I get them out and stay out, they are flying all around my basement. My kids love to take the worm farm into school for show and tell, I can’t have these guys flying all around the school. I see they like coffee, I’ll stop giving the worms coffee.
Posted 09 Jun 2009 at 8:56 pm ¶Hi Joyce,
If the worm farm stays indoors you shouldn’t have much trouble excluding any additional BSF grubs. For them to occur in your worms you either have to introduce BSF eggs or allow access to females that have mated. It’s not likely you brought eggs inside unless someone collected food scraps that have been outdoors. Mating isn’t likely indoors either, especially since you’re probably getting rid of the adults quickly.
To collect the light colored (juvenile) grubs you might try using this technique. It works even better if you find an opaque disc that fits inside because the grubs like to be under something. The “lid” should sit right on top of whatever you use as an attractant. I use moistened fish food usually, but coffee grounds, fruit, oatmeal, moistened bread, etc. will work well also. The dark mature grubs don’t eat so you can’t bait them with food. If you set the worm farm over some type of straight-walled container you can catch these grubs as they migrate away from the food in search of a pupation site. The container needs to be dry so the grubs can’t climb up the sides. The walls of the container only need to be a few inches high if they’re dry. In this photo you can see mature BSF grubs that couldn’t escape from a plastic lid because it was dry: Photo
These bugs are beneficial and harmless so if you can manage to collect them and release them outdoors you’ll be doing a good deed.
If you need clarification about anything please let me know.
Good luck.
Posted 09 Jun 2009 at 9:09 pm ¶Hi Jerry, Bong, Regina, I am based in Pasig, Philippines. Just bumped this blog today in search of cheap food for my free range chicken in Zambales. Great Blog indeed! Saw a few larvae last month in my coffee ground - carabao dung mix for my ANC wormbed and I thought they were pests so I discarded them. Had I known earlier, would have collected them. Anyways, will be wiser next time.
Posted 13 Jun 2009 at 8:48 pm ¶Just two questions for now: #1. How can one increase the colony of worms when mature BSF only mate outdoors? #2. Can I make an enclosure, say made of net, and simulate their natural environment with the purpose of a continuous system? Thanks very much Jerry for starting this blog.
Hi armand,
I appreciate the nice feedback.
1. If you keep your food source in an area that the wild BSF can access they will come to it continually and lay eggs. The main limiting factor is temperature, but I don’t think that’s an issue where you are. The best scenario is to have the BSF unit outdoors but under some type of cover that keeps rain out and fully shades it all day to avoid overheating. You can increase the size of the colony by increasing the surface area of the unit and the amount of food/waste deposited.
2. Yes, you can enclose the colony in a net, but I don’t see the benefit of it. Adult BSF females are strongly attracted to an actively feeding colony of BSF grubs so keeping them contained in an enclosure isn’t necessary for a continuous system.
Please let me know if you have other questions.
Posted 13 Jun 2009 at 9:20 pm ¶Hi, Thanks for the blog, lots of useful information and I’m now a bit more reassured about the hundreds of grubs wriggling away in my balcony compost.
Posted 24 Jun 2009 at 12:06 pm ¶However, despite all the good they are probably doing to my compost and the fact that we now have no flies buzzing around it, I’m a bit concerned about what will happen next. the compost is on my balcony so I’m worried that we are soon going to be infested my the adult flys or that my compost will always be full of the grubs - there isn’t actually any of my compost that doesn’t have grubs, so I can’t use it to fertilise or repot plants.
Any advice on how to remove them or reduce their proliferation would be helpful otherwise I fear I’m going to have to throw out all of my compost.
Hi Steve,
First let’s address your being infested with black soldier flies. I’ve raised and released tens of thousands of BSF grubs on my property over the past few years and I’ve never seen more than about a dozen of the adult BSF at any one time. In addition please consider that I’m always involved in trying to attract them. The reason they’re relatively rarely seen compared to other fly species is that their life cycle is different. Adult houseflies live for up to 30 days and during that time they need to eat of course. BSF adults only live for 5 - 8 days and they don’t eat during that period. They’re sole purpose as adults is to mate and lay eggs. When a BSF adult is attracted to any type of waste it’s almost certainly a female looking for a place to lay her eggs. For that reason the male half of the BSF population is almost never seen at all. Then, after laying her eggs the adult female BSF has no interest in the food source so she simply leaves and shortly dies. That’s the long version of “you won’t get an infestation of adult BSF”.
I’m glad that you’ve observed how BSF repel houseflies and other pest flies. That’s something I’ve addressed many times, but it’s nice to have confirmation of that from a third party.
You certainly can use the compose for repotting plants. If you separate a portion of the compost from the main pile the BSF will soon cycle out of it assuming you don’t add more food scraps to it. The BSF grubs are there for one reason, food. If the compost is in an open container the grubs will simply leave after any remaining food is consumed. If you want to have more control in removing the grubs from the compost you can use food scraps as bait and capture them using the method I describe here.
You also have the option of repotting any outdoor plants without removing the BSF. As I stated above they will simply leave when there is a shortage of food scraps. You might damage some of the grubs by handling them that way, but that’s the only downside I see.
The following post might be helpful if you haven’t already read it: http://blacksoldierflyblog.com/2008/09/15/mythbusting-black-soldier-flies/
Whatever you do please don’t throw out your compost, the BSF are harmless and the compost will have only been improved by their work.
Please let me know if you need further advice.
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