We are trying our third attempt at breeding BSF in New Zealand where our average winter min-max temperatures are 3C-11C and our average hottest month of summer temperature range is 11C-22C.
This time we brought back a 2ft x 3ft x 5ft high plastic greenhouse that someone had been using in a spare room till his new wife took over the room. It had successfully bred 3 generations. It cam with pupa, and we have had dozens of flies for a few weeks now. We have had it set with a fan heater at 28C. There is an artificial green plant for them to next in. We have them in front of a sun-facing window (in the heat of the day we half close the curtain to give it sun in half the area so it doesn't overheat). The humidity is always over 35% and often closer to 70-80% (lots of rain this year).
We have given them water and also fresh cut fruit (That they do come down and suck), and we have tried pretty much every bait to attract them - rotten fruit/ vegeis, manure, coffee grinds, old bedding and pupae shells, but we have seen no evidence of mating and no evidence of eggs.
Any other suggestions of what we can do?
We are pretty much ready to decide that they are not going to work in this climate and give up.
We want to raise food for chickens and fish. The blue worms are not sourcable here - anyone that had them had the Eisenia fetida out-compete them. I have heard mixed reports of the safety of using Eisenia fetida for food. We do, however, have Lumbricus rubellus turn up naturally wherever manure drops on the ground, and while they do breed more slowly, we could get the numbers up eventually to breed for food. We have a small container of white worms, we are slowly breeding, that LOVE our climate by reports. We are also having some early success with breeding crickets (though not locusts - of 50 starter pack, we are down to 9 over a few weeks - maybe too humid for them? the remain ones are growing and turning into adults though). We have wood chip brought in by the truckload for free, so think we have the natural diet for crickets there (as well as maybe woodlice - the cousins of roly polys that don't curl in a ball and don't attack your fruit and veges as much). Again - take a few years to breed up your supply but they do thrive in our climate.
My experience in a subtropical climate in Mexico (temp range - 0C to 35C, high humidity): uninvited BSF invaded my red wiggler habitat and persisted with no intentional support from me. The larvae went everywhere, especially before/after a big rainstorm. They were much more prolific and hardier than the red wigglers. I never tried to get rid of them, but I doubt it would have been possible. I was also never able to contain them, but I never tried one of the commercial bin options.
I would venture a guess that perhaps your genetic stock was not so great, or perhaps there was not enough genetic diversity to adapt to your conditions, or maybe you're efforts to create an ideal environment are backfiring somehow. In your position, I would get some more BSF (from multiple sources if possible) and try again. I would try less environmental control, just put them outside in a semi-sheltered area - no fan or direct sun or anything like that. Let natural selection take a shot at it, and if that doesn't work I guess I would look at different insect options.
BSF are basically tropical, or at least need reliably warm weather for several months of the year, with pupae persisting in a dormant state through winter cold. I don't ever see any flying or laying or anything until there has been a month or more of days in the high 20's C. You might try a larger greenhouse...or find someone who has a large greenhouse that might host them for breeding and you bring eggs or larvae back? The adults have an odd mating habit where the males stake out a territory and the females find them....it needs space.