I’d hazard a guess that it’s because in late season there’s less food availability for caterpillars (as foliage is starting to toughen and die back at the end of summer). Newly hatched caterpillars generally prefer younger more tender leaves, which would be widely available in spring on the Northern migration.
Nah, tons around. I’ve seen two just yesterday and today.
I am going to semi-hijack my own OP, if that is permitted. Thanks to all for the answers/clarifications provided. (I love the SDMB for just this reason).
There has been a abundance of butterflies with white wings that I see out through my window. They are not moths and they are very numerous, more than the monarchs that I have seen. They flit about so fast that I have not been able to capture them (err… poor choice of words) with my cameras. Can anyone clue me in on who they are? My google-fu returns so much that I get lost.
For those who wonder, I am on the west coast of the state of Michigan, about half-way down the mitten if you get my drift.
European Cabbage White, an introduced species.
Interesting, but I haven’t noticed any dots on the wings. I will try to get a closer look in daylight tomorrow.