If you have a standard 38 Litre Rubbermaid bin, you will probably have to harvest your vermicast at least every six months. The picture to the left demonstrates a good worm count or worms to surface area ratio and you can see some egg sacks, looks like the perfect time to harvest. The vermicast is well-developed and there is no visible food or bedding left. It’s always a good idea to stop feeding your bin one to two weeks before you plan to harvest, this will dry out the castings and ensure food and bedding is composted. You can check out this link for effective methods of harvesting, http://www.naturesperfectplantfood.com/2013/08/30/harvesting-worm-castings-from-your-bin/
The 38 Litre bin is usually harvested if; the contents are over 7 inches deep or the estimated amount of worms is high enough to present a possibility of over population. Using the vermicasting formula, 1 square foot of composting surface area to 1 pound of worms to 1 Litre of food material per week, a 38 L bin tops out at between 2.5 to 3 lbs of worms. Of course the more worms you have the more castings too, so a high worm count bin will need to be harvested more often.
If you find yourself in a position to begin a new bin, you’ll want to transfer eggs and a minimum of 1/4 lb of worms into their new environment. Young worms are hungry worms, they can eat 1/2 their own body weight every day. A hatchling will be able to produce offspring of its own in about 6 months.