Fat bodies in honey bees and insects in general are not the same as what we refer to in humans as “body fat.” Rather, they are particular organs that contain a conglomeration of protein and fat, and that act similarly to the liver in vertebrate animals,¹ with certain functions that are handled by the vertebrate pancreas, spleen, and adipose tissues.² 

In honey bees (as in all insects), the fat bodies perform many diverse tasks including pesticide detoxification and immune function.

Because they store large amounts of protein, fat bodies are also essential for long-lived healthy bees, such as those that will survive through the months of winter (diutinous bees).  Older workers rarely consume additional protein, and those that are foragers almost never do.

The role of this biological structure in honey bees was not fully elucidated until 2018, when Dr. Samuel Ramsey first presented the results of his vital experiments that overturned the long-standing orthodoxy that the mite, Varroa destructor, feeds on bee blood (hemolymph). His research proved that instead, these mites feed almost exclusively on honey bees’ fat bodies — with grave consequences to the targeted individuals and their entire colony.

Ramsey’s research offered a fresh and revealing perspective on the breadth of this mite’s impact to honey bee health and survival.  That is, he showed that the damage from Varroa’s parasitism of honey bees is associated with Ramsey’s research offered a fresh and revealing perspective on the breadth of this mite’s impact to honey bee health and survival.  That is, he showed that the damage from Varroa’s parasitism of honey bees is associated with all of the following:

“…impaired development of immature bees, decreased lipid synthesis, reduced protein titres, desiccation, impaired metabolic function, inability to replace lost protein, precocious foraging, heightened winter mortality, impaired immune function, decreased longevity, and reduced pesticide tolerance.¹

For more detail of Dr. Ramsey’s pioneering work on fat bodies and the feeding behavior of Varroa destructor, watch his 2018 presentation to a group of beekeepers.

Visit this link to read Dr. Ramsey’s more detailed technical report, “Varroa destructor feeds primarily on honey bee fat body tissue and not hemolymph,” published in the Proceedings of the National Academy of Sciences (2019).

References

1-S Ramsey et al., 2019, Varroa destructor feeds primarily on honey bee fat body tissue and not hemolymph PNAS 116(5): 1792-1801. https://www.pnas.org/doi/10.1073/pnas.1818371116

2- A Strachecka et al., 2021, Segmentation of the subcuticular fat body in Apis mellifera females with different reproductive potentials, Scientific Reports 11(13887.   https://www.nature.com/articles/s41598-021-93357-8    

3- S Ramsey, 2018, Varroa does not feed on hemolymph, WeBInar Danmarks Biavlerforening.  https://www.youtube.com/watch?v=DK2Xi0ST4rA

4- Wikipedia contributors, 2024, Colony collapse disorder, Wikipedia. https://en.wikipedia.org/wiki/Colony_collapse_disorder  

5- AL Toth and GE Robinson, 2004, Worker nutrition and division of labour in honeybees, Animal Behavior 69(2): 427-435. https://www.sciencedirect.com/science/article/abs/pii/S0003347204004051?via%3Dihub