I have 14 Monarch cats pretty close to making the pupa. I have noticed since they hatched and eating, they prefer milkweed with flowers blooming. Almost all the eggs were laid on Narrow Leaf which was and is still blooming. Plants of other milkweeds which had finished blooming got very few eggs. I have been giving them the flowers and some have spent hours eating in the flowers. I have been raising monarchs since 9-11-01 and this is the first time I have found this behavior.