Brendan, the last two summers, I had one female visit my milkweed patch each day for about three weeks. She came at the same time each day, would leave for about a half hour and then return several times to nectar and lay eggs. She did tend to lay only one egg per plant, but since I was watching and caught on to her routine, when she left, I would find the eggs and gather each leaf so that when she returned there were most plants with no eggs for her to lay some more! Most days I collected 15 - 20 eggs, but there were a few days of over 40!
Over 400 in 2014 and close to 300 last year.
If I searched for eggs early evening (I used the setting sun to help me find the eggs) I rarely found any in the early am so it surprises me that one would lay eggs over night, especially since temps may be too cool to fly.
