JANUARY
2009

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

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01-08-09

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House Warming Survival Activity for Honey Bees

As I was growing up on a farm in the state of Kansas, a bright but cold sunny day in January often prompted my father to repeat an old saw relative to weather. With an air of authority he would announce: "As the days grow longer, the cold grows stronger."

The truth in the old saying is not a happy thought. The increased amount of daylight is a sure indicator that spring is on the way, but consistent warmer temperatures will take some time to get here. Meteorologically, that is because the cold captured in frozen soil and water, especially in more northern regions, will override the increased warming capacity of the sun to determine atmospheric temperatures. At least for a few weeks.

But as is always the case following the December equinox, the sun moves a little higher in the sky each day. Thus the days get longer and the warming on our part of the earth increases. And once again the spring and summer growing seasons are upon us. In the meantime, honey bee colonies, like Boy Scouts have to be prepared. So even though the cold is stronger during January, honey bees are planning for warmer days ahead.

Honey bees, like all insects, are cold-blooded organisms that cannot function when temperatures are low. For most insects, the temperature threshold for biological activity is around 50 F. Below that temperature, not much happens in the insect world. No walking, no flying, no feeding. Furthermore, when temperatures are below 50 degrees for an extended period of time such as in winter, insects must have a mechanism for coping. Insect species that live in temperate and colder climates do.

When temperatures turn cold, most insects enter a state of suspended animation, either hibernation or diapause. A few insect species fly to warmer climes. A small number of insect species, such as cockroaches and grain beetles, live in buildings where temperatures are kept at acceptable levels.

Some social insects, such as ants, termites and honey bees, survive winters as colonies. Many ants and termites have nests deep enough in the ground so that temperatures remain at acceptable levels. Honey bees, on the other hand, live in nests above ground where temperatures frequently drop below survival levels. So how do honey bee colonies overcome the threat of Old Man Winter? They use a process known as clustering.

Honey bee clustering works this way. When the temperature drops below 57 F, the bees begin to accumulate in areas of the hive where the comb contains stored food reserves of honey and pollen. Imagine that the bees form a basketball-shaped mass.

The bees on the surface of that imaginary ball form an insulating shell 1-3 inches deep by filling all of the spaces, including empty cells in the comb. On the inside of the ball, the bees are less compact so that they can move around.

As air temperature decreases the cluster contracts in size. Conversely, as temperatures increase, the cluster expands. The heat of metabolism of the bees accumulates within the cluster. The heat produced and the expansion and contraction of the size of the cluster allows the bees to maintain a favorable temperature in spite of the air temperature.

As the days begin to get longer in January, even as the cold gets stronger, the bees begin brood-rearing, the production of young bees. This is necessary so that the hive has newly emerged bees to collect nectar and pollen when the plants begin to bloom in the spring. The problem is that honey bee eggs and larvae--like chicken eggs and baby chicks--need a high temperature of around 96 F during incubation or brood-rearing, as it is called in insects.

So if a honey bee colony has honey and pollen and if the cluster is able to maintain a temperature around 96 degrees, the queen begins to lay eggs, even in the frigid temperatures of January. All of this gives new meaning to the idea of a house warming--to bees keeping the house warm during the cold days of January is not just for survival of individual bees. It also means that the colony has a good start for success when the flowers bloom in spring and summer.

 

Writer: Tom Turpin
Editor: Olivia Maddox