Randy Oliver covers a lot of the recent research and hypotheses in a 
couple of very good summary articles available at his website. 
 Research by Maurizio (in the 50s) and others (even earlier) present a 
fairly simple model, which may not be exactly correct in all details 
and pathways, but is useful in its simplicity and practical 
application.  Her research pointed out to two types of workers, summer 
and winter, with contrasting physiologies and resulting longevities. 
 Summer workers go through the age-related duties including nurse bees 
which have high nitrogen content after feeding on pollen, resulting in 
well developed hypopharyngeal glands, which crash as feeding of brood 
exhausts their protein reserves.  These bees last weeks.  In contrast, 
winter workers develop their hypopharyngeal glands when young, but lack 
of brood rearing keeps them developed, high in protein, and long-lived, 
as in months.  

 

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