Attracting black soldier flies with corn

Apr 282010
 

Dried corn kernels soaked in water are the best bait for attracting BSF females that I have tried. I’m currently using a batch that I began soaking over a month ago. Once fermented, the corn and water give off a strong sour smell that is great for attracting black soldier fly females.

Once the BSF are established the result is a nearly odor-free process, but in the beginning it’s best to have a strong odor so the females can locate the unit. I like using fermented corn because even though it has a strong odor I don’t find it as offensive as most rotting food. It’s not a smell that I necessarily like, but it’s one I can live with during the set up phase and once I’ve got a dense colony I can go back to the normal, mild and pleasant odor of a balanced BSF composter.

One advantage of this method is that you don’t need to deal with food scraps which tend to become moldy and also attract a lot of undesired species. I did see a few fruit flies and other small flying insects in and around the corn, but compared to other baits I’ve used corn is best in this regard. Most notable is the absence of blow flies and to a great extent, house flies.

I’m using  two techniques based on this idea. I have small buckets of soured corn and water in a few places and BSF females are laying eggs in the buckets. Some eggs are laid on the bucket walls and others are laid on the dry corn that’s above the water line. The resulting larvae should be able to develop in the buckets, as long as the corn isn’t completely submerged. When there are a good number of larvae in the corn/water I’ll remove and reserve the liquid and use the corn and larvae to seed a new BSF composting unit. The corn will eventually be consumed by the larvae in the new unit and the liquid can be used alone as an attractant if needed.

The strained liquid can be used to help attract BSF females directly to new composting units. Attracting egg laying females is automatic if you have an established colony, but it is the biggest challenge in establishing a new unit. Adding the corn liquid to other scraps you place in a new unit will increase the attractive odor of the bait. Also, if you live in an area that has a limited BSF population or a cool climate this attractant might help you maintain a denser colony throughout the mating season by directing more females to your composter.

I’m sure there are many other foods that could be used in a similar way. I used corn because I can buy a 50 pound bag (22kg) for about $8 at the local feed store. The key is to develop a strong smell that will represent a food source to the female BSF who are searching for an egg laying site. I’ve been told by people in the Philippines that BSF are often found in rotting coconut meat. I imagine that if you applied the principle I described above with coconut as the base that it would also work well. Likewise, I noticed good results once after adding sour milk to a unit. Your goal should be to have a bait that you can smell from a few yards/meters away. If you can smell it from that distance the BSF will have no trouble locating your composter.

refreshing the colony

May 032009
 

restarting the colony 2009

Starting my third year with the black soldier fly

I’m going into this season with a small colony made up of grubs that were laid last fall. Where I live the winters are mild so it was fairly easy to maintain the colony through the cool months. At the end of last summer my BioPod was full of compost and I should have harvested it.  As a result of that neglect my beautiful compost became anaerobic, dense and a bit smelly. What can I say? It’s been a hectic year. :) I think early fall may be a good time for removing the BSF compost because the grubs are likely to be less active on average in winter versus the warm months. I believe the churning action of a very active colony (summer) is an important factor in keeping the compost aerated and “fresh”. I said early fall for compost harvesting because I’m afraid that if you wait too long in the season you won’t have time to rebuild the colony to near maximum size in preparation for the winter when BSF breeding stops (unless you’re in the tropics).

Spring cleaning

first BSF of 2009

BSF don’t normally land on people,
but this one had just emerged from it’s pupa so I was able to handle it.

I removed all of the compost and washed my BioPod. I hand picked a few hundred of the light colored juvenile grubs from the old compost and added them to the unit along with some fresh food scraps. I didn’t clean the grubs themselves so a small amount of the old compost was transferred along with them. This old material will act as a great attractant to BSF adults who have now started the mating season. A healthy and balanced BSF colony doesn’t have a strong or bad odor, but the females will always be attracted to the faint scent of an established colony. As I mentioned previously, my compost is anaerobic now and therefore smelly, but the typical mild smelling compost from a balanced culture would work just as well.

BioPod-spring cleaning

A new drain

As you can see from the first photo in this post I have replaced the BioPod’s liquid collection jar with a straight drain into the ground. (I hope you won’t be too disappointed with me Dr. Olivier.) I haven’t been gardening and to date I haven’t done anything productive with the liquid (also called “tea”). For that reason I’m opting for the convenience of the straight drain for now. To see how I set up the drain you can go to my “Tips and Tweaks” page.

The pond

You can also see my pond in the photo. I moved the BioPod near the pond because I’ll be feeding fish scraps and culls to my BSF colony this year. I don’t enjoy killing fish, but to maintain the population in a healthy balance I will be removing some of them. I’ll have some help from birds, turtles, and snakes, but the pond is fairly close to the house and wild predators are limited. With the BioPod I’ll be able to convert the excess fish into nutritious black soldier fly grubs and return them to the pond as fish feed. I have a post about my philosophy regarding feeding BSF grubs to other animals here.

Black soldier fly grubs are also fantastic fish bait, so having the BioPod near the pond will be very convenient for fishing. I’ve created a page about BSF as bait which you can find here.

Winter BSF culturing

As I mentioned earlier I did keep the colony going through the winter, but I didn’t keep any records. The one thing I can confirm is that the BSF grubs will interrupt their usual development during the cold season. I had very few BSF laying eggs by October and the last one I observed laid her eggs late in that month. By November I stopped seeing any smaller grubs in my colony. I assume then, that the grubs that  currently make up my colony are at least five months old. During the summer this stage would only last 2-3 weeks. Next winter I want to be better prepared to test cold weather bio-composting and I hope that some of you will participate in it with me. At the end of this summer we should start a thread about this at the BioPod forum to share strategies and results.

Logging this year’s results

My goal this year is to keep a log of all the food I add to the colony and the weight of the grubs produced. I’ll be fairly general about recording the composition of the food scraps so this won’t be a controlled experiment. The fact that I’ll be adding a large amount of whole fish and fish scraps will certainly effect my results. My goal is to provide a general outline of what you might expect. You can find the log in the column on the right of this page under Black Soldier Fly Pages, or simply click here.

solider

Trial and Error – Starting My First BSF Colony

May 242008
 

I put out my first bucket of food scraps to attract black soldier flies in the spring of 2007. I soon observed the adult flies laying eggs in my bucket so I assumed that in a few days I would see larvae.

The literature I’ve read states that BSF eggs will hatch in roughly 100 hours.

After six days of seeing BSF in my bucket I had observed what I correctly assumed were BSF eggs, but still no larvae. The evenings had been cool and I imagined that temperature was the limiting factor. I took this photo on the sixth day and you can see a group (clutch?) of eggs which are about 1/2 inch (12 mm) across:

bsf eggs on cabbage

More than two weeks after observing BSF all I had to show was a few fruit flies and some dehydrated food scraps. I wasn’t even seeing BSF anymore. At that point I began to lose interest in the project and I stopped checking the bucket on a daily basis. We were experiencing drought conditions then and the last time I had checked the bucket I didn’t even replace the lid. We finally got a good rain but since I had lost interest I didn’t bother checking the bucket. A few days after the rain I passed by the bucket and noticed some flies buzzing around. I took a closer look and saw that they were black soldier flies. I looked inside the bucket to see some sloppy food scraps, and finally, BSF larvae.

first batch of black soldier fly larvae

black soldier fly larva and a penny

The fact that some of the larvae were almost full size seems to indicate that they had hatched even before the rain. Maybe the dry conditions didn’t stop the development of the eggs but instead just slowed it down and possibly limited the number of survivors. I think it may be best to keep the food scraps shaded and moist to help the eggs develop. Also, when the larvae first hatch they’re very small and it won’t be easy to see them for several days.

My First Attempt to Attract Black Soldier Flies – May 2007

May 242008
 


As soon as I realized that black soldier flies were present around my home I put some food scraps into a bucket with a lid and cut a few small holes into the sides.

my first bucket of black soldier fly bait

BSF will crawl through a small opening to access a food source for their eggs. They don’t eat in their winged stage which is referred to as the adult stage. In fact, they don’t even have fully functional mouths because they only live a few days, just long enough to mate and lay their eggs.

I initially put out dog food, cottage cheese, bread, and assorted fruits and vegetables. Note: You can and probably will also attract ants (and most importantly, dogs) with this type of mixture so do what you can to keep these undesirable animals out of the bait. Within a few hours I had a few ladies (female BSF) checking out the offering and depositing eggs.

black soldier fly laying eggs on cardboard


If you look at the left side of the bucket in this next image you can see a BSF just before it entered the bucket through the small hole.

black soldier flies entering bait bucket

Be sure to keep the container with your food scraps out of the direct sunlight or you may overheat the larvae. If this happens they will evacuate the container if possible and if not they may die. I learned this the hard way.

An established and properly balanced container of Black Soldier Fly larvae will not have a bad odor. BSFL will consume the food scraps so quickly that it doesn’t have time to develop the bacteria that causes bad odors. If you overload the colony with food it can begin to smell before it’s eaten. A two foot diameter (60 cm) BioPod can process several pounds of food scraps each day.