It’s down to the asters and goldenrods, among the last of the blooms for pollinators to visit before it’s too cold to visit anything.
All this work, and then what happens to these insects?
The bumblebee queen who founded her colony in the spring (the old queen) and all of the workers she produced will likely die in the first freezing weather of the winter. All their work over the summer and fall was to ensure that new queens would be born and survive the winter to found new colonies the following spring. New queens hatched during the summer feed voraciously on nectar and pollen in the fall to lay down fat stores that will carry them through the winter in their underground nest.
Hoverflies (depending on the species) might overwinter as adults or as late-stage, fully grown larvae, by taking shelter in protected nooks and crannies of tree roots or bark. In Minnesota, they will have to withstand freezing solid, as temperatures drop well below zero. Individuals that overwinter as adults (probably females) are the ones we see flying around in the spring looking for aphid-infested plants on which to lay their eggs before they die. When the larvae hatch, they have a food source waiting for them. A second wave of hoverflies join the party after warmer temperatures have spurred them through the pupal stage to emerge as adults.