How to Start a Black Soldier Fly Colony from Pupae

You have three options when starting a colony: buy eggs, buy adults, or buy pupae. Eggs are fragile, desiccate easily in transit, and give you no way to verify viability until it's too late. Adults have a lifespan of only 8–14 days and reduced mouthparts, they survive on fat reserves and don't feed in any meaningful way, so every hour in a shipping box is an hour they aren't mating. Pupae are the sweet spot. They're hardy, easy to ship, and when they emerge in your setup, they're fresh, healthy adults ready to breed on your terms.

Think of pupae as colony seeds. You're not buying larvae to feed to your chickens — you're buying the next generation of breeders.

What You Need Before Your Pupae Arrive

The setup doesn't need to be complicated, but there are a few non-negotiables.

A breeding cage or enclosure. Minimum 3' × 3' × 3' — adults mate in flight, so they need airspace. A simple PVC-and-screen-netting enclosure works great outdoors. Bigger is better; 4' × 4' × 6' is ideal if you have the space.

Sunlight or bright lighting. This is the number-one reason colonies fail. If you're setting up outdoors — and I'd recommend it for your first colony — direct sunlight solves this problem for you. It's the best light source for mating, period. If you're running indoors or need supplemental light, standard shop lights, plant grow lights, and low-wattage LEDs won't cut it. You need full-spectrum light with a UV component at a minimum of 63 µmol/m²/s — practically speaking, if you can stare directly at the light without squinting, it's not bright enough. Metal halide, quartz-iodine halogen, or BSF-specific LED panels are your best bets. Run a 12–16 hour photoperiod for indoor setups.

Warm temperatures. The cage area needs to stay at or above 75°F (24°C) for adults to mate. Optimal mating happens between 81–95°F (27–35°C). Outdoors during summer in most of the US, you're already there. If you're running through shoulder seasons or indoors, you'll need supplemental heat — an Inkbird ITC-308 controller plugged into a ceramic heat emitter works well for about $35 total.

An egg collection setup. Corrugated cardboard strips positioned 1–2 inches (2–5 cm) above a container of moist, fermenting organic matter. Damp wheat bran, overripe fruit, or moist poultry feed all work great as attractants. The females lay eggs in the cardboard crevices, not in the food. A pro tip: adding 500–1,000 live young larvae into the attractant substrate provides chemical signals that boost egg-laying and helps suppress mold. Our Coop egg collection system is designed exactly for this, but DIY corrugated cardboard will get you started.

A shallow water source for adults. A damp sponge or shallow dish with pebbles works. Adults can drown in open water, so don't leave a deep dish unattended in the cage.

A larval rearing bin. Any opaque plastic tote, 10–20 gallons. Ventilation holes near the top, a ramp on one side so prepupae can self-harvest later. Our BSFL Bin Kit includes the ramp, collection insert, entrance pod, egg tree, and step-by-step instructions — just add your own bin.

Step by Step: From Pupae to First-Generation Larvae

Day 0 — Pupae arrive. You'll get dark brown, capsule-shaped casings about 18–20mm long — roughly the size of a vitamin pill. Place them in a shallow container inside your breeding cage on a bed of slightly moist coconut coir or sawdust. Don't stack them deep — a single layer is ideal. Don't poke or prod them. Keep the cage at 75–82°F (24–28°C) in darkness or very dim conditions until emergence. Mechanical damage kills pupae, so handle gently and leave them alone.

Days 7–14 — Adults emerge. At 27–28°C, expect emergence around day 14. You'll see adult flies chewing out of their pupal casings — they're black, wasp-like, about ¾ inch long, and completely harmless. No biting, no disease transmission. They're one of the most benign insects you'll ever keep. They mimic the look of organ pipe mud dauber wasps, which can be startling, but they're harmless.

Days 14–17 — Mating begins. Once emerged, adults will mate within 2–3 days if conditions are right. This is where light matters most. Outdoors in direct sunlight, you'll see strong mating activity without any intervention. Indoors, crank the lights and keep the temperature up. You'll see pairs flying in tandem — that's mating in action.

Day 18 — Egg laying peaks. Female BSF lay roughly 70% of their eggs on day 4 after emergence. Check your corrugated cardboard egg traps daily. You're looking for tiny, cream-colored egg clusters tucked into the flutes. Each female can lay 200–600 eggs in a single clutch, with some females producing up to 1,500. Replace egg traps every 1–2 days and move the loaded ones to your hatching area immediately.

Day 22 — Eggs hatch. At 80–86°F (27–30°C), eggs hatch in about 4 days. The neonates (first-instar larvae) are barely 1mm long and extremely vulnerable to drying out. Keep humidity at 60–70% and substrate moisture at 60–70% by weight — it should clump when squeezed but not drip. These first 48 hours post-hatch are the most critical period in your colony's life. Note: eggs won't hatch below about 56°F (13.6°C), so if nighttime temps are dropping, bring your egg traps inside.

Days 22–36 — Larval growth. Your first-generation larvae are now feeding and growing through 3rd–5th instar. This is the main production phase. Keep temperatures between 77–95°F (25–35°C), and feed them kitchen scraps or pre-consumer food waste at roughly 10–15% of larval biomass per day. They'll reach harvestable size (prepupae) in 14–21 days. You'll know they're ready when they darken from light tan to dark brown and start crawling up the sides of the bin — that's the natural migration instinct kicking in.

Day 36+ — Colony is cycling. You now have prepupae to harvest (for feed, composting, or drying) and adults mating in your cage to produce the next generation. The full egg-to-adult cycle repeats every 38–45 days.

How Many Pupae Do You Need?

For a starter hobby colony, 200 pupae is a solid starting point. Not all will emerge successfully, expect a 70–85% emergence rate from a good supplier. Of those, roughly half will be female. Each female lays 200–600 eggs. So 200 pupae → ~70–85 viable females → potentially 14,000–50,000 eggs in the first generation. Even with natural attrition, that's more than enough to establish a cycling colony.

Our Black Soldier Fly Pupae (200 count) are sourced from our own high-viability colony stock and shipped with care to maximize emergence rates.

The Three Mistakes That Kill First Colonies

1. Bad lighting. I can't stress this enough. If your adults aren't mating, it's almost certainly the lights, or the lack of sunlight. The easiest fix is to move your breeding cage outdoors where it gets direct sun. If you must stay indoors, upgrade your lighting before you troubleshoot anything else. Minimum 63 µmol/m²/s; most successful mating happens above 200 µmol/m²/s.

2. Low humidity on neonates. Those first 48 hours after hatch are critical. If you're in a dry climate, Colorado's winter air runs 15–25% RH indoors, and even summer in the arid West can be tough, your neonates will desiccate before they ever reach second instar. Keep humidity at 60–70% around your hatching substrate. A small ultrasonic humidifier or a damp cloth cover can make the difference.

3. Overfeeding the larval bin. New colony keepers tend to dump in too much food too fast. If substrate isn't consumed within 24–36 hours, you've overfed. Excess food goes anaerobic, produces ammonia, and the larvae will evacuate the bin entirely. Start conservative and scale up as the colony grows. If you notice a sour, ammonia-like smell, stop feeding immediately and add dry carbon material, shredded cardboard, straw, or sawdust, to absorb excess moisture and restore aerobic conditions.

What About Colorado Specifically?

If you're on the Front Range or anywhere in Colorado, you can absolutely run a BSFL colony. During summer (May–September), outdoor colonies work well, you've got the sunlight, the warmth, and wild BSF are present in the region, which means you can even supplement your colony genetics with wild-caught pupae. This prevents inbreeding depression, reduced fecundity and smaller larvae over time, which is a real issue in closed colonies.

The two things you're fighting year-round are cold and dry air. Aurora winters hit 0–15°F, so a year-round colony means moving indoors and solving for artificial lighting, supplemental heat, and humidity control. An Inkbird ITC-308 on a ceramic heat emitter handles temperature, and an ultrasonic humidifier on an Inkbird IHC-200 hygrostat handles humidity. Total added cost: about $50–80 for equipment that'll last years.

One Colorado-specific note: at 5,400 feet, lower air pressure can accelerate substrate evaporation. Monitor your substrate moisture more frequently than sea-level guides suggest, especially during our dry winters.

Ready to Start?

Starting a BSFL colony from pupae isn't complicated, but it does reward preparation. Get your cage and egg collection set up before your pupae arrive, if you're doing this outdoors in warm weather, sunlight handles the hardest variable for you. You'll have a self-sustaining colony producing larvae within 5–6 weeks.

If you want everything in one box, our BSFL Bin Kit gives you the rearing setup, and our BSF Pupae give you the colony starters. And if you get stuck, we offer one-on-one consultations to help troubleshoot your specific setup.

Questions? Drop a comment or reach out, I'm always happy to nerd out about these bugs.