Hermetia illucens, commonly known as the black soldier fly, is a widespread insect species within the family Stratiomyidae. It is increasingly recognized for its role in organic waste recycling and its potential in generating sustainable animal feed.
About the Black Soldier Fly
Adult black soldier flies measure around 15-20 millimeters (about 5/8 to 3/4 inch) in length and have a predominantly black body. Their metallic reflections can range from blue to green on the thorax, sometimes with a reddish hue at the end of the abdomen. A distinctive feature is the presence of two small, transparent “windows” on their basal abdominal segments, which contribute to their wasp-like appearance. Their head is wide with well-developed eyes, and their antennae are elongated, approximately twice the length of their head.
The larvae, in contrast, are a dull, whitish color, growing up to 27 millimeters (about 1 inch) long and 6 millimeters (about 1/4 inch) wide. They possess a small, projecting head equipped with chewing mouthparts. While native to the Neotropical ecozone, black soldier flies have spread globally and are now found across all continents. They naturally inhabit areas with decaying organic matter, such as compost heaps, carrion, and manure, but readily adapt to urban environments like dumpsters and compost bins.
Life Cycle of the Black Soldier Fly
The black soldier fly undergoes a complete metamorphosis, progressing through five distinct stages: egg, larva, pre-pupa, pupa, and adult. The entire life cycle spans about 45 days, though this can vary based on environmental conditions like temperature and food availability.
Female black soldier flies lay between 200 to 600 eggs, usually in crevices or on surfaces near decaying organic materials. These pale yellow or creamy white eggs are about 1 millimeter in length and hatch into larvae within about four days. The larval stage is the longest and most active feeding phase, lasting about 18 to 36 days. During this period, the larvae grow significantly, reaching lengths of up to 27 millimeters and weights between 0.10 and 0.22 grams, while voraciously consuming organic matter.
As larvae mature, they enter a non-feeding pre-pupal stage, which lasts about 7 days, during which they migrate to drier areas. This is followed by the pupal stage, where they remain inactive for about 1 to 2 weeks as they undergo metamorphosis. Finally, adult flies emerge, living for 5 to 8 days, primarily focused on reproduction. Adults do not feed, relying on energy reserves accumulated during their larval stage.
Transforming Organic Waste
Black soldier fly larvae are effective in the decomposition and recycling of various organic wastes, including food scraps, agricultural residues, and animal manure. Their voracious feeding habits allow them to break down these materials, converting them into biomass. This process significantly reduces the volume and weight of organic waste, often by around 50%, in a shorter timeframe compared to traditional composting methods.
The larvae contribute to environmental benefits beyond waste reduction. They can help reduce harmful bacteria like Escherichia coli O157:H7 and Salmonella enterica in manure. This bioremediation capability makes them a valuable tool for managing livestock waste and improving sanitation. Black soldier fly larvae also outcompete other pest flies, such as houseflies, for resources, helping to control their populations in waste environments.
Valuable Outputs and Diverse Uses
Black soldier flies offer valuable products and applications for various industries. Their larvae are a rich source of protein and fat, containing 40-44% crude protein and 15-49% fat, depending on their diet. This makes them a sustainable alternative protein source for animal feed, suitable for livestock, aquaculture, and pets.
Beyond animal feed, black soldier fly larvae are also considered edible for human consumption, offering a protein-rich food source with high calcium and amino acid content. The byproducts of larval processing are equally valuable. Frass, the residue left after larval digestion, is a granulated, odorless material composed of larval feces, shed exoskeletons, and undigested matter. This frass serves as an effective organic plant fertilizer, providing nitrogen, phosphorus, and potassium, and can improve soil health.
The lipids (grease/oil) extracted from black soldier fly larvae can be used for biodiesel production. Their high lipid content makes them a promising feedstock for biofuel. Chitin, a biopolymer found in the insect’s exoskeleton, can also be extracted from the larvae. Chitin and its derivative, chitosan, have applications in sectors such as food, cosmetics, and pharmaceuticals.