I breed my waxworms on a 1:1:1 mixture of Ready brek (instant porridge oats with added vitamins), wheatgerm and wheatbran (about 1 cup of each). I then add a couple of table spoons of dried active bakers yeast and bring the lot together with honey and glycerol. The glycerol stops the mixture drying out. You want to coat all the ingredients with the honey/glycerol giving you a crumbly texture that isnt too wet. You can added shaved beeswax to this but I have had great success without it.

Have them in a ventilated container with a piece of kitchen towel under the lid. The larvae can eat thru anything so My lids are ventilated with very fine stainless steel mesh. It can seem that nothing is happening and then theres an explosion of larvae!