Update Sep 25, 2017.
The last chrysalis hatched out Sep 24, 2017, after forming its pupa on Sep 03 – a total of 21 days. Photo from Sep 3rd.
Chrysalis on Sep 24, barely visible under all those Aster leaves.
The images are very poor due to difficulty parting the clump of Asters without disturbing the butterfly.
During these last days of summer, there were 2 chrysalis on Morning Glory, 2 on Meadowsweet Spiraea alba directly in front of the Morning Glories, 1 on Steeplebush Spiraea tomentosa which was next to the Meadowsweet, and 2 more in Purple-stemmed Asters which were closer to their original food plant Swamp Milkweed.
On the 24th, a total of 5 Monarch, including the last one to hatch visited the yard.
Today (Sep 25th), only one stopped by for a snack on Tall Boneset.
I suspect this is the end of their season. Bye Monarchs.