Hermetia illucens

Hermetia illucens
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Suborder: Brachycera
Infraorder: Tabanomorpha
Superfamily: Stratiomyoidea
Family: Stratiomyidae
Subfamily: Hermetiinae
Genus: Hermetia
Species: H. illucens
Binomial name
Hermetia illucens
Linnaeus

Hermetia illucens, the black soldier fly, is a common and widespread fly of the family Stratiomyidae. Neither the larvae nor adults are considered pests or vectors. Instead, black soldier fly larvae play a similar role to that of redworms as essential decomposers in breaking down organic substrates and returning nutrients to the soil/environment.

Black soldier fly larvae (BSFL), are an excellent source of sustainable protein for aqua culture/ animal feed, pet and human nutrition. As the larvae have voracious appetites they can be used for composting household food scraps and agricultural waste products.

The adult soldier fly has no functioning mouthparts; it spends its time searching for mates and reproducing.
Black soldier fly depositing eggs in cardboard

Life cycle

Black soldier fly eggs take approximately four days to hatch and are typically deposited in crevices or on surfaces above or adjacent to decaying matter such as manure or compost.[1] The larvae range in size from 1⁄8–3⁄4 inch (3–19 mm). Although they can be stored at room temperature for several weeks, their longest shelf life is achieved at 50–60 °F (10–16 °C).

The adult fly, which measures about 16 mm (5/8 inch),[2] has a life span of 5 to 8 days. It is a mimic, very close in size, color, and appearance to the organ pipe mud dauber wasp and its relatives. The mimicry of this particular kind of wasp is especially enhanced in that the fly's antennae are elongated and wasp-like, the fly's hind tarsi are pale, as are the wasp's, and the fly has two small transparent "windows" in the basal abdominal segments that make the fly appear to have a narrow "wasp waist". The adult soldier fly has no functioning mouthparts; it spends its time searching for mates and reproducing.

Black soldier fly inflating its wings during the first 15 minutes after emergence from pupation.

Uses in composting or as food for animals

Black soldier fly larvae (BSFL) are used to compost and sanitize wastes, and/or convert the wastes into animal feed. The harvested pupae and prepupae are eaten by poultry, fish, pigs, turtles; even dogs.[3] The wastes include fresh manure, food wastes of both animal and vegetable origin.

Grub composting bins use self-harvesting

When the larvae have completed their larval development through six instars, they enter a stage called the "prepupa" wherein they cease to eat, they empty their guts, their mouth parts change to an appendage that aids climbing, and they seek a dry, sheltered area to pupate.[4] This prepupal migration instinct is used by grub composting bins to self-harvest the mature larvae. These containers have ramps or holes on the sides to allow the prepupae to climb out of the composter and drop into a collection area.

Benefits

Larvae are beneficial in the following ways:

Establishing and building larval colonies

The main difficulty is obtaining black soldier fly larvae 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, it is possible to start or maintain adequate larvae colonies from native soldier flies; however, 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.

Requirements for captive-breeding chambers

Captive breeding can also keep pest flies away if done carefully.

Space and shape

Newly emerged soldier flies mate in flight.[7]

“Tingle et al (1975)… reported that mating and oviposition were observed “often” in a 3 × 6.1 × 1.8 m cage held outdoors. In addition, mating was observed in a 0.76 × 1.14 × 1.37 m cage held outdoors, but not when held in the greenhouse.”[7]

“No mating or egg collections occurred in two small cages (53×91×53 cm) and (38×46×38 cm)”[7]

More recently, captive breeding has been observed in a cylindrical chamber measuring 46 cm (18 in) diameter by 56 cm (22 in) tall for 99 litres (3.5 cubic feet). "Mating under artificial light did not occur but did succeed with natural sunlight." [8]

German scientists have successfully bred soldier flies in a space as small as 10 liters.[9][10]

Heat

“Adults typically mated and oviposited at temperatures of 24 °C (75 °F) up to 40 °C (104 °F) or more. Booth and Sheppard (1984) reported that 99.6% of oviposition in the field occurred at 27.5–37.5 °C (81.5–99.5 °F)”[7]

Light

“Minimum light intensity for mating is 63 μ mol m2s -1 with most mating occurring at over 200 μ mol m2s -1 (J.K.T. and D.C.S., unpublished data).”[7]

Humidity

“Relative humidities of 30–90% supported mating and oviposition”[7]

Human food

Black soldier fly larvae are edible to humans. The larvae are highly efficient in converting proteins, containing up to 42% of protein, and a lot of calcium and amino acids. In 432 hours, 1 gram of black soldier fly eggs turns into 2.4 kilograms of protein. They thus can be a source of protein for human consumption.

In 2013, Austrian designer Katharina Unger invented a table-top insect breeding farm called "Farm 432" in which people can produce edible fly larvae at home. It is a multichambered plastic machine that looks like a kitchen appliance. According to Unger: “Farm 432 enables people to turn against the dysfunctional system of current meat production by growing their own protein source." About 500 g of larvae or two meals can be produced in a week by the machine.

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."[11]

Black soldier fly larvae and redworms

Worm farmers often get larvae in their worm bins. Larvae are best at quickly converting "high-nutrient" waste into animal feed.[12] 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 a 100°F, 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.[13]

Possible Natural Enemies

In West Africa, Dirhinus giffardii has been found to be a parasitoid of H. illucens pupae and have a negative impact on 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. [14]

Names and trademarks

A generic term for grubs of Hermetia illucens is black soldier fly larvae, abbreviated as "BSFL". Black soldier fly larvae were developed as a feeder insect for exotic pets by D. Craig Sheppard. Dr. Sheppard 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 black soldier fly larvae and use their own brand names such as "Soldier Grubs," "Reptiworms" ,"Calciworms, and "BIOgrubs." In Australia Black soldier Fly Larvae are marketed as live feeder insects under the trade marked brand name "Beardie Grubs" at selected pet stores.

References

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