Here is a video from Cal Lomsdalen (Tarboohoneybees) of a talk given by Gerry Rozema in BC on splitting hives. The video, which talks extensively about the honey flows in our area, raises an interesting question that has intrigued me for many years: the process by which diutinus bees are produced.
At about 30-32 minutes into the video, he answers that the stimulation of the hypopharyngeal gland for jelly production to feed brood is the spark that sets in motion the 42-day cycle of the short-lived (summer) bee’s life.
This explanation makes as much sense as anything else I have heard. The bees go through the cycle of life spending about 3 weeks in the egg, 3 weeks as a brood bee, and 3 weeks as a forager (6 weeks as an adult make up the 42-day cycle). But in an eggless and brood less colony the normal cycle is broken and the last bees hatched in September and early October will stock up on protein and sugar and live through the winter. It might be counterproductive to feed bees pollen supplement late into the Fall season because it delays the broodless state allowing Varroa mites to proliferate.
This could also explain why bees bred for northern climates tend to do better because they reach a broodless state faster than Italian bees.
The talk includes a model that explains splits and the effects on both the donor colony and the split colony—a good video for everyone with time on their hands staying at home.