Some of our butterflies emerged on a cool, wet day. We decided to keep them overnight had release them the next day when the weather was better.
I was concerned about them not getting anything to eat. To feed a butterfly, make up a solution of 1:20 sugar to water.
There are lots of different recommendations on how to feed them. We tried a few different options, but have ended up either finger feeding them, or having them eat off cotton balls.
Finger feeding a butterfly is fun. Wash your hands first, then dip your finger in the sugar water. Leave a drop on your finger and move it close to the butterfly's mouth. Usually it will stick out it's tongue and have a drink. When the novelty wears off, switch to the cotton ball method.
Dip a cotton ball in the sugar water, then place it on a dish in the container. Most of our butterflies didn't figure it out on their own. Often we had to let them crawl onto a finger and then put them on the cotton ball. Once they were on the cotton ball, it wasn't long before the long curled tongue appeared and they realized there was a food source right under their feet!
Read more about raising Painted Lady Butterflies.