I have lived in the Chicago area for about 5 years now, and I have been wondering how the relatively unpredictable weather conditions during April/May (with temperatures sometimes oscillating between 35 and 70 F within hours) affect the life cycle of insects.
For example, we had a snow storm last Saturday, and as I was watching the snow violently pushed to the ground by the strong wind I kept thinking “how many of the American Ladies and Red Admirals I saw yesterday should I expect to die today? 20%, 60%?”
I’m thinking of insects in particular because I perceive arthropods as somehow less likely to resist extreme temperatures and weather conditions than most of the vertebrates living in the area; but that is just my unfounded intuition :-)
I would appreciate it very much if somebody could either provide some evidence and educated intuition about this, or/and point to research on the topic.
I couldn’t tell you for most stuff up there, but most of the very small insects and arachnids should do just fine under the snow. Snow is actually a great insulator. Lepidoptera may have a harder time as adults, but I think many go beneath the snow and pop out okay.
That makes sense. Indeed there are insects who are clearly much better equipped to survive winter temperatures and snow. For example many coccinellidae hibernate inside crevices in our building. However, I wonder what happens once they leave their hole.
I guess there is some randomness in the process so some of them will leave earlier than others, and will occasionally face winter storms in the middle of a regular Spring week. I wonder what happens to them, are they going to be ‘selected out’?
Some insects produce anti-freeze that reduce the freezing points of their bodily fluids, others seem to survive being froze by making fluids freeze outside their cells. Not sure about the mechanism that allows that. Also many insects only need hours in their adult form to ensure continuation of their line.