Black Soldier Fly Temperature Requirements

More home black soldier fly systems fail on temperature than on anything else, and usually the keeper concludes the larvae were bad.

The Warm-Climate Insect Problem

Hermetia illucens is a warm-climate species. Everything about its biology assumes warmth, and every rate slows as temperature falls.

• Feeding rate drops as it cools
• Development time stretches out — weeks become considerably longer
• Adults will not mate below the range they need, regardless of anything else
• Cold larvae go dormant, which is useful for storage and fatal for production

The Two Different Questions

People conflate these, and they have different answers.

Keeping larvae alive is easy across a wide range. Cool larvae simply slow down — which is exactly why refrigerating feeders works. Dormancy is a feature.

Breeding a closed colony is much harder, because adults need warmth and adequate light to mate. This is the step that fails in temperate-climate home setups, and it is why most keepers buy larvae rather than producing them — see can you breed BSFL at home.

What Goes Wrong in Practice

• An unheated garage in autumn. The bin works, then does not, and the keeper blames the larvae.
• A bin in direct sun. The opposite failure — overheating kills a bin faster than cold does.
• Fridge storage that is too cold. Cool storage is dormancy; genuinely cold storage kills them. A fridge, not a freezer, and not the coldest shelf.

The Practical Rule

Warm and stable beats warm and variable. A bin that swings hard between day and night underperforms a cooler bin that holds steady, because every swing costs the colony adjustment it pays for in throughput.