I live in south-central Pennsylvania. Each year we begin only seeing monarchs in late-July, sometimes early August and as a result, our milkweed has already been decimated by aphids or, is actively in the process of being decimated. Many years we’ve witnessed monarch caterpillars struggling to consume what little plant material remains; they often consume aphids in addition to plant matter. They also move from instar to instar at such a slow rate they are sometimes attempting to consume seed pods that are beginning to dry/crack (in late August/early September).
This summer the adult monarchs visiting our yard are all very small and are also faded in their coloration. I did a quick google and see that it has been proven when larvae struggle to find adequate nourishment they tend to be smaller and also less vibrant as adults.
I am curious: is it possible our smaller/faded returning adult monarchs are the same ones who eclosed in our backyard last summer - thus, they are the caterpillars we observed struggling to find nourishment?
Or…is my theory goofy…are butterflies not like herps (who - I think - return to their birth ponds to mate)?