As our upstate NY weather turns toward winter, we begin to face the essence of our research question: is it feasible for small farmers to raise BSFL year round? The species is native to warm climates in the Americas, and when temperatures dip too low (below ~70F) their metabolism and development slows down. We would like to create conditions mimicking the warm climates to ensure fast growth and development throughout our winter. Our initial idea was to keep them in a heated greenhouse where the heat from their metabolic process and breakdown of large amounts of food waste would be enough to keep larva warm enough to develop. By early November we found this was an incorrect assumption. In the winter our greenhouse gets down to 45F at night, and up to 80F during sunny days. We found that the larva were still eating, but at a much slower rate. The food waste was decomposing faster than the larva could eat it, causing a foul odor and fruit fly infestation. To address the problem we created a small heated space within the existing greenhouse. A table, covered in vaulted plastic and heated with a radiator style space heater created a greenhouse-inside-a-greenhouse (see picture). The bins on top of the table were raised on one end to allow compost tea to drain out the lower end into a plastic gutter screwed onto the table. The larva climb out the raised end into a collection tub. Two concrete blocks were placed under the legs at one end of the table, and one under the legs on the other end to let the compost tea run out of the sloped gutter into a 5 gallon bucket. This system gets down to 46F during winter nights and up to 100F during sunny days. Larva have begun to mature into flies within the system. Although we intended to have larva crawl out to be collected and moved to a separate breading area, we will leave the flies in the heated area to see if they will repopulate the bins. To test this, we put one bin in the system that contains food, but no larva. We’ll find out definitively if the flies are laying viable eggs in this system over the next few weeks. We’ll also have to wait to see if the larva metabolism rates increase with the increased heat. We designed this miniature greenhouse mostly with supplies from the farm; table, plastic from an old greenhouse, collection containers, food waste, wooden post to support plastic, and 5 gallon bucket for compost tea. Supplies purchased for this project were radiant space heater ($40), storage bins to hold larva ($10 each), and a vinyl gutter ($5).
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Black Soldier Fly - Wintering Over