Protection by Behavior

The honey bee genome project told us that honey bees have fragile immune systems with fewer genes associated with their immune system than many other insects. With the individual bees slightly protected, it seems that the honey bee evolved a number of behaviors to protect the health of the colony as a whole. On a warm winter day, with temperatures rising slightly above 50 degrees Fahrenheit, the bees leave the hive to make cleansing flights. Honey bees keep a clean nest, and they never defecate inside the hive. Today’s picture shows honey bees returning to the hive’s entrance, reduced to a small opening for the winter. Occasional warm days allow the bees to leave the hive briefly and reduce the effect of Nosema disease. Other colony health behaviors include the protection of the hive by guard bees, and workers’ removing dead bees from the hive. An important behavior for the protection of the colony involves sick or diseased bees leaving the hive to die, thus not spreading pathogens to healthy bees of the colony. The absence of sick or dead bees has made the study of Colony Collapse Disorder even more difficult.

We are learning more about the mechanisms involved in the spread of Colony Collapse Disorder. Searching for the causes of CCD and its breadth, researchers are looking into the health of native pollinators as well as honey bees. Like the honey bees, a number of these native insect species are declining. Rajwinder Singh, et al reported in PLoS ONE, December 22, 2010, on their investigation into bumblebee health. The report can be read at http://www.plosone.org/article/info:doi/10.1371/journal.pone.0014357. Singh found that bumblebees can carry viruses normally found affecting honey bees. The investigators found that the viruses are transported between the different insect species in the pollen that they collect. Over time, we will learn much about the relationship between the honey bees, the other pollinators, and the environment. This mechanism of transmission of viruses is a key part of the unraveling story.

--Richard