They are VERY small at this point. This small size is the size my birds prefer. I then place a folded piece of newspaper on top of my culture. The worms tend to crawl into the paper. They do this at about 2-3 months.
Moisture is a two edges sword.
Too little and their growth slows, too much and rot slows the culture. In this way I can be fairly sure that the bran has a chance to completely dry out before I add more moisture. To increase the nutritional value of the worms, I also place cuttlebones and insect essentials on top of my cultures right before harvesting worms. As the worms eat the cuttlebone, their guts are filled with this rich calcium source which is in turn fed to the birds. I have found this way of raising worms to be very successful.