Farfalla - The information about the effect of light on developing cats and crysalis came from "The Monarch Butterfly: International Traveler"
by Fred A. Urquhart , who did an extensive study on monarch migration and discovered the first overwintering grounds in Mexico. The book is now out of publication but can still be found at amazon.com and is filled with information on raising monarchs, migration information, and other monarch facts he learned about monarchs in his many years of dedicated research. It is the definitive textbook on Monarchs, especially if you are interested in the scientific data discovered over the years.
I do not have my copy at hand but when I do I can send you more information about how light affects maturing cats and triggers migration behavior. Tag and release information is here on site and if you have not ordered your tagging kit yet, it would be good to order now so you can have it in time to tag this year.
Jen- I put one egg in each ziplock sandwich bag with a small fresh leaf, inflated baggie before zipping it shut (a plastic drinking straw works great for this) and left them alone until I observed new food was needed and/or frass (droppings) needed cleaned out. I would check the line once a day and do whatever mainenance needed done at the time (reinflate bags, clean out frass, put in new food, or move larger cats to container big enough for metamorphis. I didn't use paper towel when a whole leaf was used, but it is needed if you just have a cutout section of a leaf as leaf fragments dry out much faster than a whole leaf. I would collect enough milkweed for several days, strip each leaf from plant, soak in a bowl of cool water, then drain and store in large baggie in fridge until needed. Leaves will keep for several days like this. I would sort them by size and keep smaller tender leaves for baby cats , and saved the larger leaves for the bigger cats. Soaking or misting the leaves before putting them in baggie seems to provide enough moisture without drowning the tiny critters. If you only have one egg or cat per bag you can leave it in there through several instars, just make sure you move it to a larger container before it is ready to change to crysalis. Hope that helps!