The reasons why BSF may not be laying eggs can be looked at from several perspectives. One reason is perhaps the mama may not be physically strong enough. They may be fed on a veggie-based diet with a lower protein content.

Some people have seen the flies go dead several hours after pupation. It may be because their bodies are relatively too weak for reproduction. Some call these the pre-mature crawl-offs.

Together, let's see why the BSF may not be laying eggs:

Reason #1: Light & Temperature

Black soldier flies love mating in early morning where there is good light source. From 9 AM to 1 PM is when the flies are most active. The light warms their body temperature well enough to get them in the right mood for mating. When the females are ready to mate, they usually stretch their tails out. Thus with good light, the males will be able to see this signal & get ready for action.

Make sure there's good lighting around your cage so they can mate & lay eggs. Naturally, the flies will gravitate towards brightly lit corners. During rainy season, although the humidity is good, it may lack some sunlight. In the winter, when they go into dormancy, the flies may not lay eggs. Some people use breeding lights to breed indoors in these cases.

Although they like some light for mating, the mama flies like to lay eggs under the shade. If you have a big breeding cage, place your egg collectors at the four corners of the cage. Or use some piece of aluminum or fabric to cover it. This signals to the flies that this is a good place that won't dry out their eggs. They may be attracted to come and lay eggs there. As they do, other females will follow as it signals to them that is a safe spot to lay their eggs.

Another aspect we can look at is:

Reason #2: The Age of the Flies

For newly pupated soldier flies, they may not lay eggs immediately. For the first 3-4 days in their short lifespan (5-8 days), they need to find a partner for breeding. Even before that, they need to develop their sexual organs. When they are fully sexually mature & find a good mate, they'll mate tail to tail.

The males will die after mating & the females will lay their eggs and then die off soon after that. Black soldier flies are also known to be notoriously hard to mate. Sometimes, the mating rate is only about 30% for one population. But it is not impossible, so be patient & don't give up hope yet.

Next, have you looked at:

Reason #3: The Density of the Flies

Make sure the density of the flies population in your BSF cage is not too high. Some people stack too much flies in one place, thinking with this space-per-fly optimization they will get more eggs per the same square space.

This has proven to be counter-productive for them. It creates a heat issue & the stacking up of flies onto each other for light and space share.

As the flies buzz around & bump into each other, they get confused. So spacing out about 10-20 kilos of fresh larvae in a 6 square meter cage would be okay. Or about 40-50 fly heads per 10 square cm. It helps because BSF sometimes mate when they are flying.

Another important aspect you can check is:

Reason #4: The Attractant

Have you checked that the attractant is good enough? Mama soldier flies love the smell of rotting or fermented matter. This means yummy food for her babies when they first hatch. Some good attractants for them are fermented food, bran, soya bean, rotting fish, chicken, meat, veggies, fermented maize etc. Some people also use chicken poop.

One farmer uses the dead bodies of the parent flies from previous generations as attractant. And ugh, it smells so bad, but according to them it works. Make sure the moisture content of the attractant is good. Around 60-70% should do the job.

BSF may not like the new foods as much as the aged attractant that they've gotten used to the smell. Some growers find that they won't lay eggs around the newer foods much but still do around the older ones. Let your attractant age & keep some of that aged stuff to keep the colony going.

Also, don't forget about your:

Reason #5: Egg Collectors

Design some good egg space or 'nests' like a stack of wood or cardboard. The concerns of the mama flies are the predators eating her eggs or the sun would dry out the moisture in them.

So understanding the concerns of the mama flies, a good egg space should protect the eggs from ants & other stuff and gives good shade to prevent the eggs from drying out. When she hasn't found a good place to lay eggs yet, she may not want to do so as chances of survival for her babies are low.

Wood stacks are good because they can retain the moisture & keep the smell well (if you pre-soak them in fermented foods or water). Watch out for rats, cats or raccoons as well if you're setting up the love cage outdoors.

See if there is any other stuff around. The flies may randomly lay their eggs into the safety gaps there or in the nests & not your desired places. This happens a lot to a lot of growers. It's because of the smell that gets diffused in the air around the growing environment. When she lays eggs there once, she'll find that same spot to lay again & again. Because she now knows it's safe for her. The other ones may follow suit.

In this case, try some fish fins or dead BSF bodies to help the attractant smell last longer. Place your attractant box somewhere without strong wind so the smell doesn't get diffused away too quickly.

And finally, something that BSF growers share is to see:

Reason #6: The Male/Female Ratio

Growers also share that the temperature that you keep the pupae (the blackened larvae) may affect the proportion of male/female in the population. Some say that there is not enough females in the population so the egg laying rate is low.

Female tend to love shaded place or cooler temperature more. From a grower's experience, keeping the pupae in the shade for about 10 days prior to placing them in the love cage (where temperature may be higher) helps produce more females to lay eggs.

Summary: For More BSF Eggs

So in summary, here are some points to consider if you would like to get eggs from your BSF colony:

  • Good food so the mama & papa have good health for reproduction
  • Warm morning light so the flies can mate easily
  • Shaded corners for the mother flies to lay eggs
  • Some newly pupated flies may need time finding a love mate
  • New flies may not develop mature sexual organs yet
  • Space out the population so it's not too dense in the love cage
  • Make attractant with strong, attractive smell for the flies
  • Design safe egg nests that's near a food source
  • Look out for ants, rats or any other places that the flies may lay eggs
  • See if your flies are thirsty & provide good hydration for them
  • Keep the population of male/female balanced
  • Check if any flies escaped when you open your cage

And by looking from these different perspectives, you may get a clearer picture on why your black soldier flies may not be laying eggs yet. Sometimes, it's the natural environment around. Sometimes, we just need to be a little bit more patient with it as things unfold. Hope this brief post has given you some ideas for fixing the issue. Good luck & have a great egg harvest with your black soldier fly colony.

Responses to Readers' Questions

What is the temperature for hatching eggs in Europe. And rearing the larvae? Should their environment be humid?

--> Thanks for your question. The hatching temperature is usually 29C.

For rearing the larvae, don't let it get too hot. Above 43C may be too hot for them, and they'll start evacuating out. They can survive temperature from 10-15C but below -6C they might not survive.

At the adult fly stage, humidity may lengthen the life span. But at the pupae stage, you'll need some dryness for them to turn into flies. When they are still larvae, a moist humid envirnoment is good for them (not overly wet). I hope this helps!

my black soldier flies are not laying eggs,,what I'm supposed to do ,please advise

--> Thanks for your question. First of all, how old are the flies now? If they have just hatched from the shells, they may not be sexually mature yet. Give them 3-4 days to develop then they may be more ready to mate. In the love cage, you could have sunlight around so the flies can mate. Also, prepare the egg collectors and attractant so the flies can lay eggs there. She's less likely to lay eggs if there's not food for her to-be-born babies. Please see & Keep us posted. I hope this helps!

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