Black Soldier Fly Life Cycle Explained
Matt GorenShare
The Black Soldier Fly Life Cycle
Understanding the life cycle of Hermetia illucens — the black soldier fly — helps you manage your BSFL effectively. Knowing which stage you are buying, how long each stage lasts, and what triggers progression helps you maximize shelf life and nutritional value.
The Four Stages
Stage 1: Egg
Adult female black soldier flies lay clusters of 500-900 tiny eggs near decomposing organic matter. Eggs hatch in 3-4 days. You will never see this stage as a feeder customer — it happens at the farm.
Stage 2: Larva (The Feeder Stage)
This is what you buy. The larval stage lasts 2-4 weeks depending on temperature and food availability. Larvae go through 5-6 instars (growth stages), growing from tiny thread-like hatchlings to plump, cream-colored grubs approximately 1/2 to 3/4 inch long.
This is the stage with the highest calcium content (9,340 mg/kg) and the highest nutritional value for your reptiles. Feed BSFL during this stage for maximum benefit.
Stage 3: Prepupa
As larvae mature, they stop eating, darken from cream to brown/black, and become harder. This is the prepupal stage — a transition to pupation. Prepupae are still edible but less nutritious than active larvae and have a harder exoskeleton. Most reptiles still accept them but some may reject the darker, harder texture.
Refrigeration delays this transition. At 50-55°F, larvae stay in the feeding stage for 2-3 weeks. At room temperature, they begin darkening within 5-7 days.
Stage 4: Pupa and Adult Fly
Prepupae burrow into soil and form a hard brown pupal case. After 1-2 weeks, an adult black soldier fly emerges. The adult fly is wasp-like in appearance but completely harmless — it does not bite, sting, or eat (adults have no functional mouthparts). Adults live only 5-8 days, long enough to mate and lay eggs.
You do not want BSFL to reach this stage. Store in the refrigerator to prevent pupation.
Managing the Life Cycle at Home
| Goal | Method |
|---|---|
| Keep larvae in feeding stage | Refrigerate at 50-55°F (extends to 2-3 weeks) |
| Slow darkening | Lower temperature slows prepupal transition |
| Use darkening larvae | Feed to reptile immediately — still nutritious |
| Prevent pupation | Use all larvae before they form pupal cases |
Are Black Soldier Flies Harmful?
No. Adult black soldier flies are completely harmless. They do not bite, sting, spread disease, or eat human food. They are not attracted to kitchens or garbage like house flies. If a larva escapes and pupates in your home, the emerging fly will simply look for a way outside to mate — it poses zero risk to you, your pets, or your food.
Black soldier flies are actually considered beneficial insects. In nature and in composting operations, their larvae break down organic waste efficiently, recycling nutrients back into the ecosystem.
Why Does This Matter for Feeding?
The larval stage is the nutritional sweet spot — highest calcium, softest body, most moisture. As BSFL darken toward prepupa, calcium content remains high but the body hardens and moisture decreases. Feed the cream-colored, plump larvae for the best nutritional profile and feeding response.
Store in the fridge, feed within 2-3 weeks, and your BSFL stay in the optimal feeding stage throughout their time in your home.
— Matt, Founder, All Angles Creatures
