September marks a significant shift in the solitary bee calendar. As temperatures begin to drop and days shorten, the frantic activity of summer gives way to something quieter - but no less important.
Nesting season is drawing to a close
For most solitary bee species in the UK, September signals the end of the nesting season. Red mason bees (Osmia bicornis) and leafcutter bees (Megachile species) have already sealed their nest cells with carefully packed provisions of pollen and nectar. Inside each cell, a larva is feeding, growing, and preparing for a long winter ahead.
The next generation is waiting
By September, eggs laid in summer have hatched into larvae. These larvae will feed through autumn, then pupate and overwinter as adults inside their sealed nest cells - not emerging until next spring. It's a remarkable feat of patience built into their biology.
What about your bee box?
If you have a BeeLife observation box, September is a wonderful time to watch for sealed cells - a sure sign your box has been successfully used. Do not disturb or open sealed cells at this stage. The bees inside are developing and need undisturbed rest through winter.
How to help solitary bees in September
- Leave bee boxes in place - moving them can damage developing larvae
- Plant late-flowering plants like ivy, sedum, and michaelmas daisy to support any remaining foragers
- Note which tubes or cells have been used - useful for next spring's planning
Looking ahead to spring
Come March and April, watch your bee box closely. Emerging adults will chew through their cell caps and begin the cycle again - one of nature's most satisfying spectacles.