If you search the web for instructions on raising mealworms, you will find as many variations as you do websites. The instructions that I list below are what I used to keep a small colony of a few thousand mealworms. This was enough to keep a constant feeding supply for my gouldian finches and the wild birds. Now that my nephew Patrick has turned this into a small business, ths size of our colony has grown to hundreds of thousands of worms. We still use basically the same method, but with a lot more trays.
I started my colony with 100 mealworms. I placed them in a plastic tray (Tray #1) with about 2 inches of wheat bran. Wheat bran can be purchased very inexpensively at a feed store. I added a piece of carrot and covered the tray with strips of newspaper. I sprayed the newspaper with water, but not enough to soak through to the wheat bran. In the dry winters, I usually sprayed the newspapers twice a day. In the humid summers I found that I didn't need to spray them as often. I usually put in a fresh piece of carrot about once a week and if any portion of the old carrot remained, I removed it.
In a month or two, the worms morphed into pupae, then beetles. The beetles layed eggs - plenty of them!
One month after the first appearance of beetles, I prepared another tray (tray #2) with fresh wheat bran, carrot and newspapers. I then moved the beetles, pupae and remaining large worms from Tray #1 to Tray #2. (Hint for moving beetles - spray the newspapers with water just before you are ready to move the beetles. Most of the beetles will then climb aboard the moist papers. Then just move the newspapers/beetles to tray #2.)
Tray #1 now contained the original wheat bran with lots of eggs (too tiny to see) and teeny-tiny worms. With a magnifying glass, I could see some of the worms.
I waited another month, then prepared a fresh tray (Tray #3) with fresh wheat bran, carrot and newspapers. I then moved the beetles, pupae and remaining large worms from Tray #2 to Tray #3.
At this point, Tray #1 had plenty of worms which I could start feeding to the birds. My finches liked the small worms. The wildbirds (bluebirds, nuthathces, Carolina wrens, chickadees and titmice, preferred the larger worms. Tray #2 now contains the eggs and teeny-tiny worms.
After a month of using Tray#1 as the feeding supply, I moved any remaining worms from this container into Tray #3 with the beetles. I then cleaned out Tray #1 and added fresh wheat bran, carrot and newspapers and moved the beetles, pupae and large worms from Tray #3 to the fresh mix in Tray #1. The worms in Tray #2 now contained worms large enough to use as the feeding supply for the next month.
I just kept this monthly rotation going, and there was always a fresh supply of mealworms for my finches and the wild birds.
