I added a rotten pear to my bins and that seemed to do the same. Gratis idea.

Glad the rotten pear worked for you. The more rotten food surface available to the worms the more effective the trick will be, depending on the actual amount of worms in your bin can dictate what method of food to use.

Update: This worked even better than expected . I harvested the bottom 4 trays and found very few worms in the process. The castings get sifted thru 1/4" screening which I have mentioned before and have been using for years, from there they are stored in 5 gal buckets till needed for use in the spring.

Another note was that in doing the harvest I also found no worms in the drain tray just castings, normally there are worms in the drain tray, wow the melon really makes the worms move, getting tired of the hash-hash I suppose.