Fat Bees: Winter Bees in the Hive

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Nature has given honey bee colonies a strategy to survive the long cold months of Winter. Winter bees in the hive are different than those found during Summer. They may look the same but workers in the Winter hive are fat bees. Or least they should be-to increase the chances of colony survival. With the ability to live much longer than their Summer sisters, healthy fat bees are different in relation to the size of the fat bodies inside them.

Honey bee hive in Winter snow with inset of  winter bees or workers with enlarged fat bodies.

Winter Bees vs Summer Bees

Worker bees make up the majority of the colony population. Those considered winter bees are produced during mid-late Fall.

They are remarkable because they can live for 5-6 months. Hopefully, from late Fall until late Winter/early Spring.

During the warm season, worker bees only live a short time – approximately 6 weeks. The first 3 weeks are spent on duties inside the hive, the last 3 are spent foraging for food. And, collecting all the resources needed by the colony.

Summer workers literally work themselves to death for the benefit of the colony. Wings become tattered and the fuzzy hairs wear off their bodies.

These insects do not repair broken parts through cell repair. Once their bee body parts fail, they are finished.

Roles in the Colony

Winter Bees are different than Summer Bees. In part, this is because those destined to live out the Winter months in the hive have a different set of duties.

The tasks of Winter bees are not as focused on gathering food. Though they may fly outside short distances on warm days. A work force of foraging bees is not a major Winter task.

Instead, hive members spend time tending to the queen bee and helping regulate hive temperatures. They also care for the small amount brood and can live up to 6 months.

Graphic of fat bee cartoon versus real bee with fat bodies an x and check.

Role of Fat Bodies in Honey Bee Health

How do we know that these winter bees are fat bees? Well, we don’t need to put them on a scale and weigh them.

Actually, fat bees refers to the fat bodies located inside the bee’s body- not an outward appearance.

Fat bodies are areas, or cell masses, of loosely united cells located throughout the body but concentrated in the bee’s abdomen. They store food reserves such as: fats, glycogen and protein.

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These fat bodies store vitellogenin. Vitellogenin increases the lifespan of bees and boosts their immune systems. Bees with high levels of vitellogenin are better able to store protein reserves.

Healthy bees with large fat bodies are better able to serve as nurse bees. These nurse bees do not have to eat as much stored bee bread (pollen) to be able to feed developing young.

This is a great thing – especially if the colony is low on stored pollen. Another factor, the quality of royal jelly fed to larva is determined by the vitellogenin levels of the nurse.

While checking your colony for honey stores in late Fall, also check the pollen stores. Likely the hive will have all the pollen they need. But, it is a good idea to check.

Varroa Predation

It was previously believed that varroa mites fed exclusively on bee blood or hemolymph. A 2019 study revealed that varroa actually feed on fat bodies.

This in part explains why they have such a devastating effect on the colony due to the important role that fat bodies play.

Workers in small winter colony of bees on comb.

Why Beekeepers Want Healthy Fat Bees

The honey bee colony starts preparing for Spring much earlier than humans. The calendar may say we have a few more months of Winter.

But, inside the hive, new baby bees are already being raised. Only healthy nurses can do a good job of feeding the bee brood.

By mid-Winter on the calendar more older bees are reaching the end of their life cycle. Population growth must get under way before warm weather arrives.

Good Winter survival depends on plentiful stores of food, a good population of bees and the right kind of bees. Healthy fat bees that give the colony its best chance for survival.

Insuring that your colonies are filled with healthy fat winter bees is not something that can be put off until Fall. Be proactive. If varroa are a problem in your hives, treat early (mid-late Summer).

Waiting until late Fall may kill the varroa on the bees. However, the damage has already been done and you may be going into Winter with skinny bees.

In my part of South Carolina, I want to have successful varroa mite treatments completed prior to August 20.

Area of worker honey bee caring for brood in colony.


What are Winter bees called?

The technical term for winter bees is “diutinus”. This term applies not only to honey bees but other types as well. These are colony members that are capable of surviving long past the normal life span of the species.

How are Winter bees different than Summer bees?

Honey bees produced in the late season have larger fat bodies in their abdomen. They are capable of living all through the long Winter until early Spring.

When are Winter bees born?

The production of winter bees takes place during the last few brood cycles of the year. (September-October) The exact time will vary somewhat depending on your climate.

How long do fat Winter bees live?

Bees produced for the Winter hive can live up to 5 or 6 months. But, the important fat bodies located inside the abdomen will shrink once brood feeding begins.

The health and lifespan of your winter bees can be affected by nutrition deficiencies and heavy varroa infestations.

Studies have found that colonies with varroa mite infestations do not fully develop into typical long-lived Winter bees.

Can bees get obese?

The fat bodies located inside the body of a honey bee is much different than what we perceive as being overweight. These important anatomical structures store fat and nutrients that help the colony make it through Winter.

Final Thoughts

Bees that live during Winter are physiologically different than those produced in Summer. Healthy Winter bees have enlarged fat bodies in their abdomens.

Ensuring your colonies are healthy and full of the right kind of bees is as important as other tactics of winterizing your hives. With proper planning, Winter beekeeping tasks should be minimal.


  • Snodgrass, R.E. and E.H. Erickson 1992. The anatomy of the honey bee. In The Hive And The Honey Bee, Dadant and Sons, Inc., Hamilton, IL. pp. 103-169.
  • Samuel D. Ramsey, Ronald Ochoa, Gary Bauchan, Connor Gulbronson, Joseph D. Mowery, Allen Cohen, David Lim, Judith Joklik, Joseph M. Cicero, James D. Ellis, David Hawthorne, Dennis vanEngelsdorp. (2019). Varroa destructor feeds primarily on honey bee fat body tissue and not hemolymph. Proceedings of the National Academy of Sciences, 116(5), 1792-1801.