Black Soldier Flies: Essential Facts and Insights

In this article, we will talk about everything you need to know regarding black soldier flies.

The black soldier fly is a sleek fly that is black in color and has metallic reflections. It originated in South America but is now found in other countries across Asia, Africa, and Europe.

Known by the binomial name H. illucens, these flies belong to the family Stratiomyidae.

In the following article, we will discuss more the black soldier fly, its lifecycle, what it eats, whether it is harmful to humans and more.

Black Soldier Flies
Black Soldier Fly Pupa

What Are Black Soldier Flies?

Black soldier flies are flies of the family Stratiomyidae. People often confuse them for moths, but like other flies, they have two wings and no stinger.

Their name comes from their black, metallic appearance as adults. The black soldier fly makes a significant buzzing noise when flying, which could appear concerning.

However, they are not dangerous to humans in any way.

You will usually spot black soldier flies around decaying plant and animal matter.

And because the larvae feed on decaying matter, black soldier flies are often used in commercial poultry and swine processing establishments to reduce the amount of animal manure.

What Do Black Soldier Flies Eat?

The adult black soldier flies do not have sharp mouthparts to feed on or bite into potential food. Hence, adult flies usually have a liquid diet where they drink flower nectar for sustenance.

On the other hand, the black soldier fly larvae have a varied diet. They can feed on organic waste, from food scraps to kitchen waste.

They also feed on coffee grounds, meat, and fish scraps.

The larvae turn all the organic and leftover food waste into animal feed. They can eat twice their body weight daily and convert and store the food they eat quickly.

This makes them an extremely nutritious feed for chickens. The black soldier fly larvae are also used as food for fish and some exotic pets.

Black Soldier Fly

Where Do Black Soldier Flies Live?

Black soldier flies, one of the 260 known species of the family Stratiomyidae, are found in North America.

Within the United States, the black soldier fly is abundantly spotted during late spring and early fall in the southeastern US.

The fly is also found in the continental US and throughout other countries in Europe, Asia, and Africa.

Habitat-wise, you will usually spot black soldier flies in areas with abundant organic waste. You will find them hovering around decaying matter, compost pits, and agricultural settings.

These moist environments are the perfect breeding spots for black soldier flies.

They will lay their eggs in places with enough organic waste to meet both their reproductive and larval nutritional needs.

Are They Harmful or Beneficial to Humans?

Black soldier flies are not harmful to humans because they have no biting mouthparts or stingers. They’re not pests or vectors of any diseases, either.

Instead, they are quite useful in three main areas – composting, food for humans, and feeding insects to animals.

Composting

Black soldier fly larvae are great composters and play a prominent role in breaking down organic waste and returning nutrients to the soil.

They are heavy eaters who can consume food, nearly twice their body weight.

They feed on organic material – food and agriculture waste and successfully convert it into nutrient-rich manure. This is done by harvesting the digestate.

They are also very useful in decreasing the weight and volume of waste.

The black soldier fly larvae increase the evaporation of the compost by the heat generated when they break down and churn the food.

Food for Humans

Black soldier fly larvae are extremely nutritious and can serve as human food. In their larval stage, they eat a lot of food and store around 50% high-quality protein.

This makes them nutrient-rich for human consumption.

They can either be consumed whole by cooking or frying them or ground into a fine powder and added to porridges or shakes for a protein boost.

Anecdotal evidence suggests that the taste of the black fly larvae is quite distinctive. They taste nutty and meaty, a little hard on the outside, but the meat inside is quite tender.

Black Soldier Fly Larvae

Feeder insects for animals

The pupae and prepupae, when harvested, can be used as food for fish, poultry, pigs, turtles, etc.

Data demonstrates that when the black soldier fly larvae are fed to chickens, there is an increase in productivity, i.e., they lay more eggs. It is also known to improve gut health.

At this stage, the larvae are extremely nutritious, having been voraciously fed.

They can be stored at room temperature for a long time and used as feeder insects when required.

Black soldier fly larvae are often compared to mealworms since they are popular insect feeders.

However, the reference lies with black soldier flies, given that they have a higher protein content and can also provide usable calcium to your poultry.

They are far healthier than mealworms.

Additionally, black soldier fly larvae are far more sustainable to farm than mealworms. They use less space and less water, and they leave a lesser carbon footprint.

And they produce nearly twice the amount of protein as compared to mealworms.

Black Soldier Fly Life Cycle

Black soldier flies go through four stages of metamorphosis, as described below.

Laying Eggs

An adult female black soldier fly has a life cycle of around 45 days. The adult female flies lay eggs in moist crevices close to decaying organic matter or compost.

These eggs take about four days to hatch. The eggs are oval-shaped and can be pale yellow or creamy white.

Larvae

The eggs hatch and the larvae feed on the decaying matter around them. Larvae are long and whitish.

They have a projection on one end that serves as a mouth and helps them chew their food.

Larval development is finished in about 14-18 days, during which the larvae feed voraciously.

As adults, the black soldier fly does not eat anything and instead uses the food stored during the larval stage.

In some cases, the larval stage can also extend and the life cycle be delayed because of the unavailability of the right kind, amount, and temperature of food.

Within the larval stage, the post-feeding or prepupal stage lasts for a week.

Pupation

And when it is time to pupate, the larvae move away from the moist spaces and find dry areas where they can start to pupate.

The external skeleton hardens and becomes dark in color. Within the shell, the pupa begins to develop. The pupal stage lasts for around two weeks.

Black Soldier Fly Larvae

Adults Emerge

Once the adult fly emerges from the pupa, it is ready to mate within two days.

The black male soldier flies to look out for the female soldier, who flies mid-air, and the couple often descends while copulating.

The males also use lekking sites, waiting for the female soldier fly to come.

If another male fly wanders into the territory of the resting male fly, a fight ensues to throw the intruder out.

Once mated, the black female soldier fly will find the ideal spot in dead and decaying matter to lay her eggs. The adult female fly can lay around 500 eggs at a time.

Adult black soldier flies can live longer in captivity if provided with abundant sugar or flower nectar.

Black Soldier Fly Farming

Black soldier fly farming is widely done to create animal feed.

In this process, the eggs of the black soldier fly are placed in containers filled with residual organic matter such as agricultural and food waste.

Under controlled climatic conditions, these eggs hatch quickly and feed on the organic matter around them.

The supply of food and temperature is regulated to ensure the maximum, optimal growth of the larvae in a short span of time.

Once they have fed enough and are ready to move on to the next phase of life, they are harvested and dried to be made into insect meals for further processing.

Since they rapidly consume nutrients from organic waste, the larvae are extremely rich sources of protein for animals to consume.

How Do I Get Rid of Black Soldier Flies?

While black soldier flies are virtually harmless, they can become a nuisance.

The best way to eliminate the flies is by eliminating their breeding source. The black soldier flies lay their eggs in and around decaying organic matter since that is what their larvae feed on.

If you have a compost pit or decaying, moldy food lying around, it’s best to eliminate it to end the black soldier fly nuisance. You can also use a fly swatter or an aerosol spray to kill the flies.

Regarding the larvae, if you spot them anywhere in your house, you can pick them up and discard them.

Interesting Facts About Black Soldier Flies

  1. The black soldier flies are the only true terrestrial species in the Family Stratiomyidae. Most other species spend half their time in water and half on land. Black soldier flies, however, spend their entire life on land.
  2. The adult black soldier fly does not feed. The only thing it consumes is flower nectar. It utilizes the fat stored during the larval stage for sustenance during adulthood.
  3. Black soldier flies are also forensic flies as they usually hover over dead bodies, trying to lay eggs. What makes them unique is they arrive on a dead body much later, i.e., 10 days after death. This unique timeline can answer important questions in an investigation.

Wrap Up

Black soldier flies are a very popular insect species. 

Their larvae are extremely helpful in turning organic waste into nutritious manure and fertilizer, which can greatly improve soil health.

The dried and dead larvae are further used as animal feeders for poultry, pigs, fish, and even turtles.

In some cases, even humans can eat these insects because they are so nutritious.

Thank you for reading.

Frequently Asked Questions

Are black soldier flies harmful?

Per se, black soldier flies are not harmful at all. They are not carriers of diseases, and they do not sting or bite us. But they might transfer some diseases from the rotten compost around which they fly. Moreover, if used as feeders, they can transfer metallic or lead poisoning to any animals that they are fed to.

What is black soldier fly used for?

Black soldier fly larvae are excellent composters, consuming organic waste and producing nutrient-rich manure.
They also have potential as human food, with their larval stage containing around 50% high-quality protein.
The pupae and prepupae can be used as food for animals, improving gut health and increasing productivity.
Black soldier fly larvae are more sustainable to farm than mealworms, using less space and water and producing almost twice the amount of protein.

Are black soldier fly larvae harmful to humans?

The black soldier fly is commonly found around decaying organic matter and is used to reduce animal manure in commercial facilities. While they are not known to transmit diseases, adult soldier flies can potentially carry pathogens. Accidental ingestion of their larvae is a more likely negative interaction for animals and humans.

What kills black soldier flies?

To get rid of black soldier flies, it’s best to eliminate their breeding source by getting rid of decaying organic matter where they lay their eggs. This includes compost pits and moldy food. Fly swatters or aerosol sprays can also be used to kill the flies. If you spot larvae, pick them up and discard them.

Are soldier flies aggressive?

Soldier flies are beneficial in helping decompose garbage and controlling other insect pests, but their presence in a home is usually unwanted and may indicate an unsanitary situation. Breeding sites for soldier flies include decaying vegetable material, dead animals, or bee nests. The best way to control them is to eliminate their breeding source. The larvae are harmless and can be picked up by hand, while adult flies can be killed with a fly swatter or insect spray.

Authors

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  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

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  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

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