You might encounter little tiny white spheres the size of a pinhead after your bin has been set up awhile. I first thought these were worm eggs, but it turns out they are mites. Actual worm cocoons look like brown popcorn kernels. The mites are a nuisance, but they don't harm the worms directly, although they can start to outcompete them for food if you let them get out of control. The mites are a sign that you are keeping your bin too moist. They seem to like sugary foods, like apples and banana peels. The way I combat them is to sprinkle a layer of really dry bedding on top of the food if I add alot of really moist sugary stuff. The worms can still get to the food from below, but it seems to make it harder for the mites. Then I place a slice of apple or something similar out in the open in the top tray, and let the mites collect on it, and just throw them away. You'll never completely eliminate them once you have them, but they're not a big deal to keep under control.