| Hermetia illucens | |
|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Diptera |
| Family: | Stratiomyidae |
| Genus: | Hermetia |
| Species: | H. illucens |
| Binomial name | |
| Hermetia illucens (Linnaeus, 1758) |
|
The black soldier fly, Hermetia illucens, is a common and widespread fly of the family Stratiomyidae, whose larvae are common detritivores in compost heaps. Larvae are also sometimes found in association with carrion, and have significant potential for use in forensic entomology.[1]
Black soldier fly larvae (BSFL) may be used in manure management, for house fly control and reduction in manure volume. Mature larvae and prepupae raised in manure management operations may also be used to supplement animal feeds.[2]
BSFL are sold as live pet food for owners of herptiles and tropical fish, or as composting grubs. They store high levels of calcium for future pupation which is beneficial to herptiles.[3]
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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.[4] 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 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. The adult's life span is 5 to 8 days.
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. The wastes include fresh manure, food wastes of both animal and vegetable origin.
BSFL will reclaim many nutritious elements, although they will also bioaccumulate toxic metals such as lead and cadmium if these are present: "Hermetia larval digestion of swine manure reduced nutrients as follows: N-71%, P-52%, K-52%, Al, B, Ca, Cd, Cr, Cu, Fe, Mg, Mn, Mo, Na, Ni, Pb, S., and Zn were reduced 38 to 93%."[5]
When the larvae are done growing, they enter a stage called "prepupae" wherein they cease to eat, they empty their gut, their mouth parts change to an appendage that aids climbing, and they seek a dry, sheltered area to pupate.[5] This prepupae migration instinct is utilized 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.
BSFL are beneficial in the following ways:
The main difficulty 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. BSFL will lay clusters of eggs in the edges of corrugated cardboard or corrugated plastic. In some regions it is possible to start or maintain adequate BSFL 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. BSFL 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 BSFL colonies from eggs deposited by "wild" soldier flies (which they may have released).
(Captive breeding can also keep pest flies away if done carefully.)
“Newly emerged soldier flies mate in flight."[8]
“Tingle et al (1975)… reported that mating and oviposition were observed “often” in a 3 x 6.1 x 1.8 m cage held outdoors. In addition, mating was observed in a .76 by 1.14 x 1.37 m cage held outdoors, but not when held in the greenhouse.”[8]
“No mating or egg collections occurred in two small cages (53 x 91 by 53cm) and (38 x 46 x 38cm)”[8]
More recently captive breeding has been observed in a cylindrical chamber measuring 46 cm (18") diameter by 56 cm (22") tall for 99 litres (3.5 cubic feet). "Mating under artificial light did not occur but did succeed with natural sunlight." [9]
German scientists have bred BSFL in a space as small as 10 litters.[10][11]
“Adults typically mated and oviposited at temperatures of 24 C (75.2 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 C to 37.5 C (81.5 F to 99.5 f)”[8]
“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).”[8]
“Relative humidities of 30-90% supported mating and oviposition”[8]
Worm farmers often get BSFL in their worm bins. A few have complained of foul odor, perhaps resulting from anaerobic conditions brought about by the quick release of liquids with inadequate drainage or sorbents. BSFL tend to convert "high-nutrient" waste quickly into animal feed. Redworms are better at converting high-cellulose materials (paper, cardboard, leaves, plant materials except wood) into an excellent soil amendment.
Redworms can thrive on the residue produced by BSFL, but most attempts to raise BSFL and redworms in the same container are unsuccessful. As the BSFL colony grows, the heat or activity drives the worms down while the excess liquid can create unlivable conditions for the worms. One hobbyist reported that when using a worm bin with the bottom cut off and buried partially in the ground, "worms" are able to survive under BSFL.
As a feeder species, BSFL are not known to be intermediate hosts of parasitic worms that infect poultry, while redworms are host to many.[12]
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" and "Calciworms."