The Varroa destructor mite is a honey bee parasite that feeds much like a tick on the body of a bee. The mites are about the size of a pin head, dark brown in color and visible on close inspection.
This bee mite probably arose in the Eastern or Chinese Honey Bee population and hopped over to the United States in 1987. They quickly infested western or European honey bees. One sign of infection is the presence of bees with deformed wings. Also, sometimes seemingly healthy colonies become ill and the complete hive collapses in about two weeks.
"The native Chinese bees do not have the same problems," says Dr. Xiaolong Yang, post doctoral researcher in entomology and plant pathology, who raised bees in China. "I do not recall seeing deformed wing bees in the Chinese bee. Chinese honey bees have grooming behavior which can remove the mites from the bees. They get rid of the mites."
While researchers know that the Varroa mite is behind the death of bee colonies, the mechanism causing the deaths is still unknown. Yang and Dr. Diana L. Cox-Foster, Penn State professor of entomology, now believe that a combination of bee mites, deformed wing virus and bacteria is causing the problems occurring in hives across the country.
"Once one mite begins to feed on a developing bee, all the subsequent mites will use the same feeding location," says Cox-Foster "Yang has seen as many as 11 adult mites feeding off of one bee. Other researchers have shown that both harmful and harmless bacteria may infect the feeding location."
Deformed wing virus is endemic among honey bees in the U.S., although when the European bees became historically infested with this virus, is unknown.