Years ago i had a pet store and also my own private collection of reptiles. I used to raise mealworms so i could have freshly hatched mealworms to feed baby herps that were just too small to handle the ones from the commercial growers. The castings went into my houseplants and they did great. So if you get them for free, go for it. Now as far as which is better, mealworm or earthworm castings, my intuition says earthworm. My reasoning goes like this: The digestive process is different. The mealworms eat 'meal' a mixture of grains etc. They convert the sugars and protein pretty much directly into their own protein and fat. With the earthworm, they can do the same to some degree if the particulate size is small enough. However they mainly rely on microbes to break down the cellulose and macrostarches of their foods into sugars and amino acids in a form they can absorb. The resultant feces is filled with microbes that seem to have an extra beneficial effect in garden soil. You can look up some studies on this and comments of mucous-like compounds that offer surfactant effects, etc.

Thing is, worms don't really move if there's food where they are even if theres new food elsewhere. So it can take a LONG time for all the worms to move to where you want them. I moved away from bins mainly because of the harvesting reason. BTW everyone has their favorites but I love the Worm Inn. Very breathable, no stacks to move, and the stuff out the bottom is nice and consistant. No wet VC. But to your harvesting problem, you could try this method. http://www.youtube.com/user/TheCompostGuy#p/u/25/BhyTzhPtJcg Add a small layer of VC you want done every couple of days until is all done. One advantage is it's based on running with the new system so you can spead it out for as long as you want.

I put mine near a tree that they often frequented, not anywhere near the nest box. They found it quite quickly, and use it often during nesting season. If you leave out a bowl, most likely the mealworms will be eaten by everything else. I originally started out with the feeder on my deck, but the chipmunks would get in and take them all. So I mounted mine on a post with a guard, and use 1 1/2 inch wire openings on the sides so only the small birds can get it. Here is a picture of my original feeder (before I switched to a wire sided one). I have never had a chipmunk or squirrel get past the guard. I hope this helps.

You're absolutely correct, Anita. I never put any type of food source near the nestboxes for that very reason. No point in giving Mr. and Mrs. Blue the problem of having to defend their nesting territory from hungry birds. House sparrows here eat mealworms as well, so I've had to be crafty about feeding the blues--we have multiple mealworm feeders but only the blues and the Carolina wrens know about the one out front! You know, when I took over one of the bluebird trails I currently monitor, several of the nestboxes had metal catfood cans nailed to the top--I'm sure the previous monitor used these to put mealworms in. Taking the cans off the nestbox rooves was my first renovation--definitely not a good idea because other birds also like mealworms--that was a fight waiting to happen. Kathy