The role of fat bodies in bee health
All insects have fat bodies—tissues that contain lipids, glycogen, triglycerides, and some protein. Fat bodies store and release energy according to the demands of the insect. The energy stored within these tissues is especially important during larval growth and other periods when feeding is restricted.
The metabolic action of fat bodies is often compared to the vertebrate liver because they store nutrients and synthesize proteins, lipids, and carbohydrates that circulate throughout the body. In another similarity to the liver, fat bodies detoxify nitrogenous waste products which they extract from the hemolymph (blood-like substance) of the insect.
Summer honey bees, which live only 4 to 6 weeks, have very few fat bodies. However, winter bees have large numbers of fat bodies distributed throughout the abdomen. Presumably these help the winter bees to live the 4 to 9 months until spring, and help provide the energy needed by the workers to keep the internal cluster at 93 degrees F.
Similarly, bumble bee queens eat as much as possible before winter in order to enlarge their fat bodies. These reserves must sustain them through the winter hibernation period much like the fat accumulated by a bear. So although bumble bee queens hibernate and honey bee colonies do not, both are dependent on fat bodies to see them through the winter.