I start looking for the eggs on the undersides of the leaves at the beginning of July and have found them up to the middle of August.
Last year, I noted that the numbers were WAY down. I also had some problems with larva cannibalism and vowed to nurture each larva in its own container until it was big enough to join others.
So far this year I hadn't found a single egg and was starting to get very worried that I may not get to rear any monarchs at all this year. The milkweed flowers have bloomed and their fragrance has been intoxicating. But with the heat wave we're currently experiencing, the monarchs finally seem to be arriving.
I found the first egg this morning. Hurray!
Assuming the eggs were laid recently, they will hatch within 3 - 5 days. As I will be bringing them into the house where it will be cooler, I'm hoping they'll hatch later than sooner. I bring them in to protect them from birds and insects that love to eat them and so they'll have the best chance to complete the metamorphosis to adulthood.
Skip and I are going to be taking off on another adventure tomorrow so I'm hoping to leave the stems of the leaves in water so they'll stay fresh.
The larvae emerge by chewing their way through the egg casing. Once out, they turn around and eat the rest of the egg casing then begin dining on the leaf they're on. They'll still be very small so won't be eating vast quantities for a week or so. I think they'll be fine until we get back on Friday.