To make a good black soldier fly love cage, we can measure out the space, the enclosure materials, the density of flies, etc. Let's see some ideas to get started.
A quick first note: A love cage for black soldier flies is a place for them to mate and lay eggs. In some design, people also place the hardened black pupae in the cage. So it serves a third purpose as a place for pupation.
Now let's see what material to use to build the bsf cage:
Aspect #1: Material
A smaller-opening mesh screen is better for the walls & roof of the cage. With a bigger-sized mesh, the female flies may be able to poke through and lay her eggs randomly in the net. Once she lays her eggs in that place, others may follow. Because the smell signals to them that that is a safe spot for eggs.
The tighter the aperture, the lesser the air movement around the cage. It helps retain the smell of the attractant for a few more days. Also, it helps keep some humidity inside, which could extend the life span of the flies. A good screen may also block big water droplets to slip through.