The black soldier fly, Hermetia illucens, is a true fly farmed commercially in many countries primarily as a source of food for animals or to be used as a useful protein supplement to add to livestock feed, for example, as an addition to poultry, pig, shrimp, and fish food. The larvae are often sold as live or frozen food for pets like reptiles and birds. Black soldier flies are not currently used for human food, mainly due to legal restrictions. Also, the black soldier fly larvae are excellent at converting organic waste into valuable compost.
The Nutritional Composition of the Black Soldier Fly
The flies are rich in many vital macronutrients and micronutrients. Black soldier fly larvae contain up to 42% crude protein and up to 35% fat. The fly itself has the potential for use as human food, mainly since it is an excellent source of protein and has many amino acids present. The larvae contain many essential and non-essential amino acids, and their tissues contain many vitamins such as vitamin E and provitamin D and various healthy plant chemicals such as flavonoids and healthy fats.
These insects have the added benefit of not accumulating toxins like pesticides in the body, meaning they are safe for use as live food for animals and for adding to livestock feed.
Life Cycle of a Black Soldier Fly
The black soldier fly has a so-called holometabolous development. It has 5 stages: egg, larva, prepupa, pupa, and adult. The larval form, also called the maggot stage, is most frequently used for commercial feed for other animals and as live food for reptiles and other small animals.
A female fly lays about 500 eggs near a food source, and these eggs hatch in 2- 4 days. The larval stage lasts between 12 to 22 days, and the pupa stage lasts between 8 to 10 days. Adults only live about 9 days, and the focus for adults is on mating and egg-laying. In tropical conditions, the entire life cycle can be completed in 28 to 29 days. The temperature strongly influences the duration of each of the stages in the life cycle.
Black Soldier Fly Farming
Black soldier flies can be raised on a wide range of organic waste. The type of organic waste that is used influences the body composition and nutritional content of the larvae. Larvae get water from the food, which can be kept at about 76% humidity. This ensures at least 97% survival of larvae. The waste-to-biomass conversion rate for black soldier flies averages to 22.9%, with peaks of 40%. Factors like temperature, larval density, feed quality, and quantity greatly influence this value.
Indoor or Outdoor Farming?
Black Soldier flies can be reared in an outdoor environment, but this is best done in warm but not too hot climates since the survival is compromised at a very high temperature. Furthermore, development is slowed down by colder temperatures. Flies thrive between 27°C and 30°C, while most soldier flies die at 36°C.
Since this species is endemic to the subtropical Americas, it is possible to set up and farm soldier flies outdoors in subtropical climates, where temperatures are hot enough for most of the year. In temperate countries, flies would to survive and procreate in summer, but the development would be very slow. The cycle would be halted in winter, and there would be no production possible. Soldier flies should be farmed indoors when outdoor temperatures are not conducive to an efficient and productive farm.
The adult stage of the black soldier fly can be housed in any type of mesh cage or even a complete room that is well sealed off and environmentally controlled. Temperature between 27°C and 30°C and relative humidity of 80% is ideal conditions for black soldier fly breeding. Some genetic strains need sunlight for mating behaviour, but artificial light will usually do under 36W neon tubes or 10W LED lights. Ideally, water is provided in some way, either by a misting system or small dishes. It is important to provide landing space, or the flies will drown. Many types of egg-laying material can be provided; cut corrugated cardboard is the most accessible. To make oviposition more likely, the humidity for egg-laying should be kept between 60% to 70%.
Once eggs have been deposited, the clutches on the egg medium can be carefully removed and suspended over a layer of wheat middling that is kept moist. Larvae can be maintained at a density of 10,000 individuals/m2 and fed a mixture of foods, including alfalfa, wheat bran, and cornmeal. Around 1000 larvae can be placed in a 50 liter plastic container. To avoid anaerobic conditions, the substrate depth in larval containers must be less than 10cm deep.
Once larvae pupate, they can be removed and placed into eclosion chambers with shredded paper or sawdust as a substrate. Chambers can be made using glass jars covered with a muslin cloth. Once pupation is complete and adults emerge, they can be transferred into adult flight cages.
Black Soldier Fly Processing
If there is a need to harvest larvae as live food, they can be kept alive and maintained at a temperature of 40°C, which will arrest their development, halting pupation. For use in animal feed, larvae are killed by boiling or maceration. After that, the insect biomass can be either dried thoroughly or first split up in fats, proteins (and potentially chitin). The drying process can be achieved in more than one way. The most straightforward way is by placing them in an electric or gas oven. In tropical countries, small larvae can be dried by placing them in the sun, but it can take about 17 hours at a temperature of about 38°C to achieve an acceptable drying level.
Also, the larvae can be dried in batches:
- microwaved in batches of 0.25kg for 15 minutes at 180°C
- 4kg batches can be sand roasted for 30 minutes at 150°C
- an oven can be used and heated to 65°C to dry 30kg for 24 hours
Once dried, the larvae need to be ground up before being added to feed or used as animal feed. Larvae can also be stored for many hours at -18°C.
Forecast Black Soldier Fly Yield
As a black soldier fly producer, you want to measure critical control points and identify discrepancies before issues arise. By controlling different variables such as feed type, densities, temperature, humidity, the optimal amount of light to increase hatch rates, cycle speed, conversions, and the nutritional composition with Cogastro software, you can increase yield by 40%. The software provides real-time yield estimates, feed conversion rates, cycle speed, hatch rates, and other vital metrics. You may compare historical data based on batch, substrate, and other possible variables and track performance that results in more informed decision-making.