Hermetia illucens

Common and widespread fly of the family Stratiomyidae

Hermetia illucens, the black soldier fly, is a common and widespread fly of the family Stratiomyidae. Since the late 20th century, H. illucens has increasingly been gaining attention because of its usefulness for recycling organic waste and generating animal feed.

This species is native to the Neotropical realm, but in recent decades has spread across all continents, becoming virtually cosmopolitan. It is present in most of North America and Europe, including the Iberian Peninsula, southern France, Italy, Croatia, Malta, the Canary Islands, and Switzerland, and on the Black Sea coast of Russia in the Krasnodar Territory. It can also be found in the Afrotropical realm, the Australasian realm, the east Palaearctic realm, the Nearctic realm, North Africa, Southern Africa, and the Indomalayan realm.

The adults of H. illucens measure about long. These medium sized flies have a predominantly black body, with metallic reflections ranging from blue to green on the thorax and sometimes with a reddish end of the abdomen. The second abdominal tergite has translucent areas, from which the Latin specific epithet derives. The head is wide, with very developed eyes. The antennae are about twice the length of the head. The legs are black with whitish tarsi. The wings are membranous; at rest, they are folded horizontally on the abdomen and overlapped. These eggs are typically deposited in crevices or on surfaces above or adjacent to decaying matter such as manure or compost, and hatch in about 4 days. Freshly emerged larvae are long, being able to reach a length of and weight of by the end of larval stage. adapting to diets with different nutrient content. The larval stage lasts from 18 to 36 days, depending on the food substrates provided to the larvae, of which the postfeeding (prepupal) stage lasts around 7 days. The length of larval stage can be delayed by months due to low temperature or lack of food. Adults can live typically 47 to 73 days when provided with water and food, such as sugar in captivity or nectar in the wild, or survive for about 8 to 10 days on fat reserves gathered during larval stage when water is provided. The larvae are produced and processed in industrial scale insect factories globally by biotechnology companies such as InnovaFeed and Protix, the latter operating the world's largest insect factory farm in the Netherlands.

Black soldier fly larvae are used as feed. The harvested pupae and prepupae are eaten by poultry, fish, pigs, lizards, turtles, and even dogs. The insect is one of the few insect species approved to be used as feed in aquaculture in the EU. At the pupal stage, black soldier flies are at their nutritional peak. They can be stored at room temperature for several weeks, and their longest shelf life is achieved at .

Records of human consumption of H. illucens are difficult to find. It is a multichambered plastic machine that looks like a kitchen appliance and can produce of larvae or two meals in a week. The taste of the larvae is said to be very distinctive. Unger: "When you cook them, they smell a bit like cooked potatoes. The consistency is a bit harder on the outside and like soft meat on the inside. The taste is nutty and a bit meaty.

BSFL can be used to produce grease, which is usable in the pharmaceutical industry (cosmetics, surfactants for shower gel), thereby replacing other vegetable oils such as palm oil, or it can be used in fodder.

BSFL can be used to produce chitin. Chitin is used in shipping as an agent against biofouling. It is also used in water purification.

The residues from the decomposition process (frass) by the larvae comprise larval faeces, shed larval exoskeletons, and undigested material. Frass is one of the main products from commercial black soldier fly rearing. The chemical profile of the frass varies with the substrate on which the larvae feed, but in general, it is considered a versatile organic plant fertilizer due to a favorable ratio of three major plant nutrients nitrogen, phosphorus, and potassium. The frass is commonly applied by direct mixing with soil and considered a long term fertilizer with slow nutrient release. Next to its nutrient contribution, the frass can carry further components that are beneficial for soil fertility and soil health. One of them is the soil improver chitin

Debate is going on whether the frass from BSFL rearing can be used as a fertilizer in a fresh state or has to undergo further composting before its application. Some assume that further composting would lead to the reduction of potential phytotoxic properties. In the European Union, insect frass has to be treated for one hour at before commercialization for safety reasons, whereas the same applies to animal manure in general.

The larvae of H. illucens were used in a bioremediation experiment, in which they used up to 49% of dry weight corn leaves polluted with cadmium or zinc, for 36 days.

It has been stated that H. illucens larval gut microbiota represents an optimal ecological niche for isolating enzymes and microbial strains with optimized plastic degrading ability.

H. illucens could be a feasible feedstock for biodiesel production.

The main difficulty in farming is obtaining BSFL or eggs to start or replenish the colony. This is usually done by enticing the soldier flies to lay eggs in small holes over the grub bin. Adult flies lay clusters of eggs in the edges of corrugated cardboard or corrugated plastic. In some regions, starting or maintaining adequate larvae colonies is possible from native soldier flies, but pest species such as houseflies and blowflies are also drawn to many of the foods used to attract soldier flies (such as fermented chicken feed). In tropical or subtropical climates, they might breed year round, but in other climates, a greenhouse may be needed to obtain eggs in the cooler periods. The grubs are quite hardy and can handle more acidic conditions and higher temperatures than redworms. Larvae can survive cold winters, particularly with large numbers of grubs, insulation, or compost heat (generated by the microorganisms in the grub bin or compost pile). Heat stimulates the grubs to crawl off, pupate, and hatch, and a great deal of light and heat seem to be required for breeding. Many small scale grub farmers build their larval colonies from eggs deposited by wild soldier flies.

Newly emerged soldier flies perform the beginning of their mating ritual in flight. The male grabs onto the female, and then grasps the female's ovipositor with his genitals. They mate while stationary and connected. German scientists have successfully bred soldier flies in a space as small as 10 liters.

Adults typically mated and oviposited at temperatures of or more. Around 99.6% of oviposition in the field occurred at .

Quartz iodine lamps have been successfully used to stimulate mating of adults. In particular, mating success of reared black soldier fly can be dramatically increased by exposing the adults to light that is particularly rich in wavelengths near 440 and/or 540 nm and has an irradiance that is an appreciable fraction of the intensity of full sunlight. In tropical conditions, morning direct sunlight is optimal for emergence, mating, and egglaying, with indirect sunlight often preferred before and after mating.

Humidity at 70% is considered optimal for all stages of their lifecycle. Substrate was found to be unnecessary for pupation, but substrate is thought to act as a regulator for humidity, which prevents desiccation. A 93% emergence rate was observed when humidity was held at 70%.

Redworm farmers often get larvae in their worm bins. Larvae are best at quickly converting "high nutrient" waste into animal feed. Redworms are better at converting high cellulose materials (paper, cardboard, leaves, plant materials except wood) into an excellent soil amendment. Redworms thrive on the residue produced by the fly larvae, but larvae leachate ("tea") contains enzymes and tends to be too acidic for worms. The activity of larvae can keep temperatures around , while redworms require cooler temperatures. Most attempts to raise large numbers of larvae with redworms in the same container, at the same time, are unsuccessful. Worms have been able to survive in/under grub bins when the bottom is the ground. Redworms can live in grub bins when a large number of larvae are not present. Worms can be added if the larval population gets low (in the cold season) and worms can be raised in grub bins while awaiting eggs from wild black soldier flies. As a feeder species, BSFL are not known to be intermediate hosts of parasitic worms that infect poultry, while redworms are host to many.

BSFL were developed as a feeder insect for exotic pets by D. Craig Sheppard, who named the larvae Phoenix Worms and began marketing them as pet food. In 2006, Phoenix Worms became the first feeder insect to be granted a U. S. registered trademark. Other companies also market BSFL under such brand names as NutriGrubs, Soldier Grubs, Reptiworms, Calciworms, BIOgrubs, and Obie's Worms (Canada). In Africa, they are marketed as live feeder, meal and oil by ProtiCycle for animal feed, pet food for dogs and cats, and food for fish such as tilapia and catfish.

In West Africa, Dirhinus giffardii has been found to be a parasitoid of H. illucens pupae and decrease egg production. It has been found to reduce stocks by up to 72%. The parasite is carried by the wasps and precautions should be taken to protect the larvae from exposure to these wasps. Also the Chalcididae Eniacomorpha hermetiae has been described as a parasitoid of H. illucens that may negatively impact efforts of mass production in Africa.