Category: Bee Biology

Fat Body

Honey bees have what is called a “fat body” which is a section of tissue that holds fat cells, as well as glycogen, protein, and high concentrations of mitochondria and enzymes. The fat body is the equivalent in insect terms of a mix of a liver and fat storage.

During larval state, the fat body covers most of the larvae. The fat body will quickly and efficiently store nutrients during the larval stage to be used during the pupae stage (while the bee is not fed) and the adult bee will emerge with a fat body only in her abdomen.

The fat body is extremely important for winter bees (aka fat bees). Winter bees have a bigger fat body that would allow them to store more energy and nutrients that will last for months. Summer bees have a smaller fat body and in some cases almost non-existent.

Why is fat body important?

Recent studies on the parasitic varroa mite found out that the varroa mite is not actually sucking hemolymph (bee blood) our of the larvae and the honey bee, but it’s actually eating fat body cells, which are higher in nutrients. Different experiments determined that the mite could not extract enough energy by sucking hemolymph (which has a lower concentration of nutrients) and that it would not be as detrimental to bee health to lose some hemolymph.

By taking fat body cells, the varroa mite can take a higher nutritional material that would allow for fast growth and reproduction. Taking fat body is more detrimental to the honey bee colony’s health, especially over the end of the season when the mites feed on what were supposed to become winter bees. The winter bees that fed varroa mites have a smaller fat body and will not be able to survive for as long as the colony intended when raised those bees.

This explains some of the abrupt colony collapses that beekeepers find by the end of fall when stronger hives (big in numbers and resources) end up dying before even getting to winter.

 

Foraging for water and its uses

Honeybees, like any other animal, need water to survive.

While the flowers produce nectar, the bees can obtain carbohydrates (sugar) and water out of the nectar itself. Nectar is a watery sweet liquid with sugar concentrations around 20% (water concentration could be from 35 to 85%).

When nectar is not available or the amount of water from the nectar is not enough, honey bees will have to forage for water to cover their needs.

Water foragers have a specific skill set since foraging for water is a little harder than foraging for nectar.

Bees will have to store the water in their crop (or honey sac or honey stomach). The crop is the first reservoir where liquids are stored and can be kept separated from the digestive system (by closing the proventricular valve).

To forage for water, the honey bee will have to take only enough honey/nectar from the hive to consume during transit and arriving at the water source with an almost empty crop. As she takes water in, any remaining sugar in the crop will be diluted. She now has to make it back to the hive, by consuming carbohydrates that are stored in her body, without being able to consume any calories from her water-filled crop.

Once she arrives at the hive, she needs to get in contact with other workers to pass the water to them, so she can empty her crop and take some honey/nectar to replenish her energy.

Honey bees need water to:

  • cool down the brood area on hot days (evaporative cooling)
  • increasing moisture in the brood area
  • diluting stored honey for consumption
  • making of royal jelly (about 67% water)

Honey bee brood is very sensitive to relative humidity levels. Optimum brood-rearing requires 90 to 95% relative humidity (RH). If RH is below 50%, the eggs cannot eclode (emerge) and die after three days. With RH levels below 80% or above 95%, there is a significant drop in eclosion success (many eggs fail to dissolve their outer layer and turn into larvae).

As beekeepers, it’s very important to provide water sources for our own bees. Not only because it’s hard on the bees foraging for water, but also to prevent our backyard bees to bother neighbors.

And while talking about preventing our bees to visit neighbors, it’s always a good idea to provide multiple sources of water:

  • plain water – just regular tap or well water
  • chlorinated water – if any neighbor has a chlorinated swimming pool, you should add a source of chlorinated water to prevent your bees visiting his pool
  • salted water – to provide for minerals. Otherwise, they may visit neighbors with horses or visit watering bouls from dogs (to get the salt out of their saliva droplets)

You can see below a picture of our yard watering station. We placed it right next to the garden faucet.

The in-ground plastic insert contains regular water. It also gets refilled when it rains. We added some holes on the side of the plastic tank, to make sure that the water never covers the rocks. The bees need landing spots where they can safely walk to the water line (honey bees drown easily if they fall into the water).

The metallic container is a chicken waterer where we added some mineral salts (table salr works, but we used minera salts sold in farm supply stores). The rocks were added to make sure the bees land safely. This salty water location provides the bees with minerals so they won’t bother our neighbor horses and dogs: