How to collect Black Soldier Fly eggs

I'm currently working on my new BSFL composting bin and will soon post the pictures and maybe a video if I have time to get at it. Meanwhile, I thought some of you might be interested in the subject and would like to start getting some BSF eggs to also start their journey into BSFL composting.

So a little reminder: female Black Soldier Flies are attracted to smelly food and would oviposit (deposit) their eggs on a dry material adjascent to the food. By smelly food, I'm not talking about stinky food like garbage, I'm more talking about food that have a strong smell such as coffee ground for example. The stronger the smell the better as they will sense it from afar. A great and simple recipe is just mixing used coffee ground with soaked dog kibble. There have been research on dog food to make their smell attractive to the dogs and this seems to attract BSF as well. You can also use some fruits, but that would also attract a lot of fruit flies, or meat but that would attract a lot of house flies. What ever you do you might still get those annoying house flies and fruit flies in the first couple of weeks running a BSFL bin but as their population increases they will overpower the other maggots and will also secrete some pheronomes that seem to deter other flies.

Now that you have your BSF attractant you need to find a container. It could be a simple 1 gallon (4 - 5 litres) bucket or any other container. Put the attractant mix in and install the container in a shady location in your garden. Mine has been installed just next to my outdoor worm bins.

You now need an egg trap. Female BSF can deposit their eggs on plastic surface but they will be more attracted to a better material. An easy way to make an egg trap is to take a pair of scissors and cut 5 strips of corrugated cardboard of roughly 6 x 2.5 in (15 x 6cm). Note: make sure the flutes openings are on the longer sides so you have a lot of holes in the cardboard strips. Now stack the 5 strips together and hold them into place with a rubber band. You should end up with a block of 6 x 2.5 x 1 in (15 x 6 x 2.5 cm). Using a wire string or a double sided tape, suspend this block of corrugated cardboard above your attractant, something between 2 and 4 in (5 - 10 cm) should be good. If the female finds the trap is a safe place to deposit her eggs then bingo! The more of the flutes are exposed the better as this will give choice to the females. I notice some of them would lay their eggs in the largest flute while some other prefered the squished ones.



Another variation is to roll the cardboard strips into a sort of cake as you can see below:


One more variation is to use a nail that you would heat the tip with a candle and punch holes into a section of a pool noodle:


In the photos above, the container was the leachate collection tray of a commercial worm bin. But it can be anything from simple to fancy. Here is another one I did with small bucket with a hole in the lid that fits a PVC pipe connected to a T junction. The cardboard trap is wrapped around the PVC pipe that goes through the lid.


You will need several consecutive warm sunny days for the BSF to mate and deposit their eggs so don't be surprised if you don't get anything for several days if the weather is bad.

If you want to check the trap on a regular basis, choose evening or night time to do so to avoid disturbing the trap. If you want to take some photos of the female ovipositing then you have no choice but come during the day and take the risk of slowing down your egg trapping process. Maybe a compromise would be to wait until you see a first cluster of eggs before chasing for pictures.

Here is how an egg cluster in a corrugated cardboard flute look like. The yellow/cream one on the right is a freshly laid cluster of eggs while the two brownish on the left are empty egg shells.


Alternative attractant ingredients

  • some fermenting fruits
  • animal manure
  • BSF larvae, yes adding some actual larvae if you do have some also acts as an attractant as the female adult flies are attracted by the scent of larvae (pheromones)

Harvesting existing eggs

Instead of building traps, you might be lucky and find eggs in your garden if you already have a compost pile or worm farm. Manure and food scraps added to these systems might naturally attract BSF females. You could also harvest the larvae and add them to the BSF trap you are building to make your trap even more attractive to the females.

Related videos

Good luck! If you have any questions please contact me via the comments below or thru my contact page.

Posted in A day in a worm farm, Black Soldier Fly Larvae on