Based upon others experiences as well as my own (relative newbie) with a bin, I would use something other than onion as bait. For whatever reason the onions seem to be ignored by worms until most anything else is consumed.

What do you want the worms for? Starting a bin or something else? If for something else your idea should work fine, just use a bait more attractive to worms like... well, most anything other than onions ;-) Probably avoid really acid stuff like citrus fruit as well. Most anything else that is rotting should work great.

If you wish to start your own bin you should be fine if it is an outdoor bin, but if indoors you may want to buy EF redworms as these are regarded as the most bin friendly. There are other redworms out there, but don't adjust to bin life quite as well. Some even have a tendency to be all happy for awhile and then one day decide to move on which as I am sure you can imagine leaves a mess on the floor ;-) Might work OK though, don't know. Just depends.

If you take a pitchfork and dig around the edges you will probably find some worms. If you wet a small part of the pile, say 4 ft area every few days a lot of worms will move into that area. especialy if you put some desert there like laying mash or some kind of feed.

actually one of the best worm traps is a half melon placed upside down - wet an area of the pile down as said, scoop a hollow to work the melon skin into, check in a few days or a week and there'll be lots under it - the bag trick will be slower, but would work if you put some partly decomposed mixed food waste in, and the mesh bags that citrus come in works well, but yeah, hold the onions, and citrus too, either has to be well decomposed and microbially active to interest worms

also, you'll find the most worms low in the pile and not far in, so you could just scoop into the bottom area with a pitchfork and there'll be quite a few in every fork full you turn

Bill

Thanks! I'm building a temporary bin -- it's actually a raised bed that I'm using as a compost heap. I'm going to add worms, fill it until it's overflowing, then start filling the next raised bed. When the first is mostly castings, I'll collect as many worms as I can get out of it and move them into the next bed. I'll add other organics to the first bed and plant it.

Thanks for the advice on worm bait -- I'll see if I can't get a nice overripe melon from my buddies at the produce market!

Val