|It was unseasonably warm during the past week, and
people noticed ways heat can affect monarchs and migration:
Shorter Flowering Season
Flowers go through their life cycle more quickly when it's warm:
"The heat wave is stalling here and the stiff goldenrod in the pasture is fast maturing; the flowers are finishing up." Hartley, IA
Monarchs can complete their life cycle more quickly in warm temperatures. Until there's a killing frost, they can continue to develop.
"Perhaps we'll get an extra generation after all," noted Pat Swerkstrom in Minnesota.
"The first caterpillars are just beginning to show up. This is the first year in memory with no caterpillars to start school," observed a teacher at Long Island School in Maine.
There's much to learn about roosting behavior, including whether it's temperature-driven. If so, this warm fall season may be another reason we've had so few roosts reported. Gregg Lee shared a hypothesis based on his observations in Texas. He thinks monarchs are less likely to form roosts in warm temperatures:
"We have had hundreds feeding on Liatris in mid-October, but they did not move to trees after sunset. In these cases nights were relatively warm. They did not move closer together, and definitely were not in bunches, but were located every few feet within liatris patches of many acres."