Water has several uses in a honey bee hive. During certain times of the year foragers find a source of water, fill their crops, and ferry it home. The number of bees foraging for water depends on the needs of the colony. If the in-hive workers accept the water quickly from the foragers, the foraging bees sense that the need is still high, and they will go back for another load. If the in-hive workers are slow about “unloading” the water, the foragers sense that the need for water has lessened and fewer bees will return for more.
Bees find water in a number of places including damp rocks, branches, muddy puddles, pond edges, and drops adhering to vegetation. They swallow the water and store it in their crops before flying home. The water is transferred to the waiting in-hive workers through the process of trophallaxis—the direct transfer from one bee to another.
Bees rarely store water, but bring it in as needed. In the heat of summer it is used for evaporative cooling. The water is spread in a thin film atop sealed brood or on the rims of cells containing larvae and eggs. The in-hive workers then fan vigorously, setting up air currents which evaporate the water and cool the interior of the hive. The process is similar to the human-designed air conditioner.
Nurse bees, who feed the developing larvae, also have a high demand for water. The nurses consume large amounts of pollen, nectar, and water so that their hypopharyngeal glands can produce the jelly that is used to feed the larvae, and to a lesser extent, other bees in the hive.
A third use for water occurs in the winter. Stored honey—especially honey high in glucose—tends to crystallize as it dries. Bees need water to dilute the crystals back into liquid before they can eat it. The same occurs if a beekeeper feeds crystalline sugar to bees as a winter supplement: the bees need to dissolve the crystals before they can eat the sugar.
Urban beekeepers face a problem when their bees select the neighbors’ swimming pools, bird baths, or hummingbird feeders as a water source. Although this occasionally happens, the bees’ need for additional water is less during nectar flows because the nectar contains a high percentage of water. Urban beekeepers can provide a source of water if they wish. Bees seem to prefer water that has some growth in it—such as green slime—rather than perfectly clean water. Some scientists speculate that the reason is simply that the bees can smell it and recognize it as a water source. Chlorinated pools were scarce during the last 80 million years, so bees didn’t evolve to recognize the odor.
Another problem with water collection occurs in agricultural areas where plants are treated with systemic insecticides. Bees collecting water from guttation drops—drops of water that naturally seep from the tips of stems and leaves—can be poisoned. Worse, sublethal doses of pesticide can be carried back to the hive and fed to the developing larvae by way of the nurses. Researchers are currently trying to determine the type and frequency of damage this may cause to honey bee colonies.