Learn more about the life cycle and development stages of the black soldier fly

The life cycle of the black soldier fly, also known as Black Soldier Fly or Hermetia Illucens , extends - depending on the conditions - from several weeks to months. Depending on the definition, up to six relevant developmental stages are known, which we will examine in more detail below.

The black soldier fly originally comes from tropical and south-tropical climates with generally warm temperatures and high humidity . In the wild, it is assumed that the life cycle of the black soldier fly is about 2 months. Depending on conditions such as temperature, food supply, humidity and light influences, the time periods of the different development stages often vary considerably.

Due to domestication and production in closed breeding systems, increasingly shorter cycles and development phases are observed in this interesting insect species. So let's dive into the life cycle of the Black Soldier Fly.

Eggs | The first 3-5 days | Week 1

The life of the soldier fly begins with the laying of egg packets by the female fly immediately after mating. After about two to three days after mating, the eggs have matured in the female and are ready to be laid. The eggs are preferably laid in dry places, but close to moist, rotting substrate .

The flies are particularly attracted to objects such as honeycomb cardboard or constructions made of wooden slats with special corners, gaps and edges for laying eggs. Within ten minutes, the female fly places her egg packet in suitable, protected places. One egg packet per female contains up to 800 fresh larval eggs.

After about 2 days, the egg packets begin to "dissolve" and the eggs migrate independently - ideally directly - into the prepared, very moist food substrate. The incubation of the young larvae has thus begun.

Young larvae | another 6-8 days | Week 2

In most cases, the egg packets with the carrier material are stored directly over moist feed substrate. It is important that the carrier material remains dry and clean and is not contaminated by bacteria and microorganisms from the substrate mass during hatching.

Within three to five days after the eggs are laid, the young larvae hatch from the eggs and immediately begin feeding in the moist feed substrate mass that attracts them. The newly hatched young larvae are very sensitive and must be protected from drying out by sufficient moisture in the feed substrate and, above all, by an ambient humidity of at least 50% RH .

Young larvae need about a week to grow to a size of about 4-5mm by the end of the 2nd larval stage . This is the phase in which they are usually separated from the remaining substrate (food and excrement) and transferred to the next fattening stage (3rd-5th larval stage) .

Fattening larvae | another 12-16 days | Week 3-4

Fattening larvae in the 3rd to 5th larval stage process waste materials such as fruit and vegetable scraps for about 2 weeks before they reach the 6th larval stage as brownish prepupae. This period is the period of maximum food intake and weight gain.

It is particularly important at this stage that the stocking density, the number of larvae per cm2, is well chosen so that the mortality of the soldier fly larvae during rearing is reduced to a minimum. Around 10 larvae/cm2 with a substrate height of around 20 cm has proven to be a good guideline.

Before the larvae enter the 6th larval stage and activity decreases, the larvae reach an average weight of about 0.15g per specimen . In this stage, the soldier fly larvae have the highest nutritional content and are particularly attractive as food larvae for chickens, fish, reptiles and rodents. After this, the larvae increasingly move into the brown prepupal stage and prepare for pupation.

Pupal stage | between 7-12 days | Week 4-6

After molting, at the end of the 5th and last light larval stage, the transition from the prepupa to the pupal stage begins. This is the phase in which the larvae gradually stop feeding , acquire the brown coloration and look for dry places to pupate.

This phase is also often used for harvesting, as it is possible to harvest the larvae yourself at this point. Before they pupate completely, the larvae search for a dark, dry place on their own. If you give them help in the form of a ramp from the rearing container, you can collect the prepupae separately from the substrate . As long as the pupae are still moving and are soft and moist in composition, they are good for feeding.

However, the dark larvae stop being active after a few days and freeze. At this stage they are already in the pupal stage, from which the next generation of flies will develop within one to two weeks.

Adult fly & re-laying eggs | another 7-21 days | weeks 6-9

Pupated larvae remain in a warm, dry place protected from light for about one to two weeks before flies hatch from the pupal bodies.

In controlled rearing, the prepupae are covered with litter or mulch in a dark hatching container so that optimal conditions prevail. Newly hatched flies become active after a few hours and look for bright places with plenty of light .

Two to three days after hatching, the flies are sexually mature and begin to mate, provided they find suitable conditions . The slightly smaller male grabs the female in flight and leads her to the ground. The insects then copulate (mating) when both bodies connect with each other via the abdomen.

In order for the flies to be encouraged to reproduce, they must find a suitable environment. What is particularly important here is sufficient , high-quality light , warm temperatures of at least 25°C and sufficient humidity between 60-70% RH .

After successful copulation, the eggs in the female of the next generation have matured and are ready to lay eggs. The eggs are then placed in optimized laying locations. The soldier fly's life cycle begins again.