5 Common Reasons Why Your Black Soldier Fly (BSF) Won’t Lay Eggs and How to Fix Them

When I first started Black Soldier Fly (BSF) farming, I was excited about all the possibilities there were, but, like many beginners, I quickly ran into a few problems. One of the biggest challenges was getting the adult flies to lay eggs consistently. Believe me, it can be frustrating when everything looks right, but you don’t see any eggs. Over time, through a lot of trial and error (and I mean a lot), I figured out why this was happening.

So, if you’re a beginner or you’re experiencing the same problem, here are five reasons why your BSF might not be laying eggs, based on the experiments I carried out when I first got into this journey. I hope my mistakes can save you some time, effort, and unnecessary stress.

1. Not Enough Sunlight or UV Light

One of the first things I learned in BSF farming is that light is super important. BSF adults need a lot of light to become active, mate, and eventually lay eggs. In their natural environment, this light comes from the sun, but if you're farming indoors (or if you're in a region where the sun isn’t always reliable), the flies might not be getting enough UV exposure to trigger their mating instincts.

When I started, I thought my BSF setup was fine because it was outdoors. Turns out, the flies weren't getting enough direct sunlight because the area I picked was shaded for most of the day. It wasn’t until I moved the breeding area to a sunnier spot that the flies began to lay eggs properly. Alternatively, if you’re farming indoors, you might need to install a UV light to mimic natural sunlight.

Takeaway: BSF thrive in environments with 12 to 16 hours of sunlight or strong UV light every day. Make sure your setup has enough exposure to light, or invest in UV lights if you’re indoors.

2. Wrong Temperature and Humidity

BSF are picky about their environment. They love warmth—think tropical levels of heat. The ideal temperature for them to lay eggs is between 25°C and 35°C (77°F and 95°F). If it’s too cold, they might not mate, and no mating means no eggs. I learned this the hard way when I set up my farm in an area that cooled down a lot at night. It turns out that temperature drops at night were preventing the flies from breeding successfully.

Humidity is another important factor. BSF love moist environments, with a relative humidity between 60-80%. If your setup is too dry, they won’t lay eggs. During one of my tests, I realized the humidity in my area was too low, and I had to introduce misting to keep the area moist. Just a small change like misting made a huge difference in their egg-laying behavior.

Takeaway: Keep an eye on both temperature and humidity. If the temperature drops too low at night, consider adding a heat source. Also, try to maintain high humidity by misting the area if needed.

3. Wrong Egg-Laying Material

Now, let’s talk about where the flies lay their eggs. BSF females are very particular about where they deposit their eggs. They are usually drawn to moist, rotting organic material. When I started, I thought any random pile of food scraps would do the trick. Because I was so conscious of smell, i used some fruit scraps. Spoiler: it didn’t.

I realized the material I was using wasn’t attracting the females. The problems? It wasn’t moist enough, it was not foul-smelly enough and it wasn’t close to where the flies were gathering. BSF females like to lay their eggs close to—but not in—the organic matter. So, you need to make sure that the material is attractive enough for them to choose it as a nesting site.

Takeaway: Use moist, nutrient-rich organic matter like compost or animal manure to attract BSF females. Keep the egg-laying site close to where the flies are most active, but make sure it’s not too wet or too dry.

4. Overcrowding in the Breeding Area

This was another issue I ran into. You’d think that the more flies you have, the better, right? Well, not quite. It turns out that overcrowding can stress out your flies, and this stress can reduce their mating activity. If there are too many adults in a small space, it leads to competition, and they just don’t behave the same. In fact, they can even start avoiding egg-laying altogether.

At one point, I had too many flies in my breeding cage. After a bit of research, I realized that reducing the number of adults in the space increased their activity and led to more eggs being laid.

Takeaway: If your BSF breeding area is too crowded, reduce the number of flies to give them more space to move around, mate, and lay eggs comfortably.

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5. Dehydration (Not Enough Water)

This was a surprise to me. BSF adults don’t eat solid food, but they still need water to survive and carry out their reproductive duties. I didn’t pay much attention to this at first. I thought the flies would be fine without much water. However, as it turns out, without adequate water, the flies can get dehydrated, which reduces their energy and affects their ability to mate and lay eggs.

To solve this, I began providing water sources in the form of small shallow dishes or lightly misting the breeding area to keep the flies hydrated. It wasn’t long before I noticed an improvement in egg-laying.

Takeaway: Always make sure your adult flies have access to water. You can place shallow dishes of water in the breeding area or mist the environment lightly to maintain hydration levels.  It can be as simple as using a shallow plate stuffed with very wet cotton wool. This way, the flies can be watered without drowning.

When I first got into BSF farming, I had no idea that egg-laying could be such a delicate process. The flies need the right environment, the right light, the right temperature, the right humidity, and even the right egg-laying material. And don’t forget about giving them enough space and keeping them hydrated! Each small factor plays a huge role in determining whether or not your flies will lay eggs.

So, if your BSF aren’t laying eggs, don’t panic. Take a step back and go through these potential issues one by one. Troubleshooting can take time, but once you understand what’s going wrong, it’s much easier to fix. Trust me, once you get everything right, you’ll start seeing those eggs roll in—and the reward is worth the effort.

 

Have you experienced any of these issues on your farm? Or maybe you're dealing with something else? I’d love to hear your experiences or answer any questions you have in the comments below! Let’s learn from each other and keep growing together as a community of insect farmers. Don’t forget to subscribe to Perisseia Insect Hub for more tips and updates on BSF farming!

P.S:This post is based on my own experiments when I first started BSF farming. Hopefully, my experiences can help you overcome some of the challenges I faced. Happy farming!