I read this statement that follows by (my former professor) Chip Taylor in the Monarch Watch newsletter. (Greetings, Chip!) Concerning this year's migration, "I've been searching for words to describe this migration and for ways to explain it, but I'm not sure that I can. The words that come to mind are atypical, late, slow, sparse, and undefined." Not sure I agree with the late part, as migration here started on time, but I certainly agree with the other characterizations.
I generally take a long walk through the nature reserve where I work between 16:00-19:00 hr. each day, when the weather cooperates. Almost daily sightings of monarchs, mostly nectaring at (native) thistles and asters in our prairie plantings and old fields, form the basis of my admittedly informal observations. The single word to describe this year's migration I have settled on and have been using in relevant conversation is "diffuse". The migration began here in east-central Missouri with low numbers around the time I normally see the big wave, September 9-10. A slow but steady stream of roughly the same number of butterflies drifted through daily throughout September, then abruptly dropped off around October 1.
The breeding season was also atypical here. Monarchs flew in late April through mid-May. I saw a few newly emerged monarchs flying about late-May through early June, then none from mid-June to mid_August. I can count on one hand the number of monarch larvae I saw this summer on any of the several native milkweeds that grow in the reserve.
Each year I plant a patch or two of Asclepias curassavica in my garden to attract monarchs, and until the last 10 days of August, these plants remained unscathed by monarchs (or any other sort of milkweed insect)! Then suddenly, as August drew to a close, the whole patch was being defoliated by dozens of monarch caterpillars. These pupated in September, many hanging off eaves, window and door frames of my house. As I came home for lunch each day (the house is on the nature reserve), one or a few monarchs could often be seen hanging off the moulted chrysalis. One day, the chrysalis over my screen door "hatched", and as I came up the porch stairs, it stretched its abdomen away from its hind wings, produced a large drop of meconium which fell to the door step, then fluttered down to a patch of asters in the garden.