bee biology

A time for every purpose: temporal castes in honey bees

Besides having two physical castes, honey bees also have several temporal castes.

Physical castes are based on morphological differences—in other words, the structure of individuals in each group is different. For example, you only need to glance at a queen and a worker to see they are dissimilar.

Temporal castes, on the other hand, are based on temporary periods of highly specialized work. The work is so specialized, in fact, that it requires changes in the physiology of the individual. This phenomenon is called temporal polyethism.

For example, nurse bees and comb-building bees are both workers. Structurally, they look the same. But nurses have highly developed hypopharyngeal glands that allow them to feed the developing larvae. Comb building bees have shrunken hypopharyngeal glands and lose the ability to provide brood food but produce large amounts of wax instead.

The process is not well understood. On the surface it appears that a worker bee goes from one job to another in a more or less orderly fashion, with each temporal caste lasting a week or so. But in times of stress, bees will revert to previous jobs if necessary for colony survival.

Some researchers say that if a bee can go “willy nilly” from one job to another, there is no temporal caste system. Others point out that stimuli from inside the hive are causing the changes to occur—not individuals—and that the type of physiological changes that occur define temporal polyethism.

To make it all the more complicated, spring and summer bees have a very distinct division of labor, whereas winter bees tend to be generalists. We know that the physiology of winter bees is different from spring and summer bees, so perhaps temporal polyethism does not occur in winter bees at all. The debate is far from over.

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  • Truly fascinating! How has no one commented on this in 6+ years? It is interesting what you say about winter bees. Earlier you mentioned they live longer than their warm weather sisters and half-sister. So I would assume in spring the winter bees would develop into one of their temporal castes.

    I have learned so much about bees from your blog so far. Started at the beginning and clicking to the newer ones!

    • Raul,

      Thank you for reading my old posts. I think some of my best are old, but they get buried and no one reads them.

      As for the winter bees, they die off in spring and are replaced by regular workers.

  • So why are there 3 types, not more? If winter workers have differentiated physiology and behavior, why are they not considered a separate caste? Is this just a limitation of our terminology?