Is there a reason they are bouncing back John?
Sorry for the late reply, David. I have not heard about any reason in particular. There is a lot less use of insecticides in Canada and I presume also in the USA. So, perhaps more members of each generation are surviving to continue the migration North into Canada? It could also be the weather has been sunny enough and wet enough, all at the same time. It's been a nice, hot summer with lots of sunshine; but, no drought. 'Lots of rain, too. The grass has remained nice and lush/green all summer. Perhaps the Milkweeds are thriving because of having enough water and the other factors (heat, less insecticide in the environment, etc.), are all contributing to help....a kind of Monarch Butterfly "perfect storm". Whatever the reason, it's nice to see this big bounce back. I see Monarchs flitting around my yard every day. Other years, I was lucky to see one or two Monarchs in the entire summer!