Honeybees and Varroa Mites
Asiatic Honeybee Mites Spread Worldwide Infesting European Honeybees
The varroa mite of honeybees sweeps through hives and kills bees. The parasite has spread from continent to continent.
The varroa mite, Varroa jacobsoni (also often called Varroa destructor) is a dangerous parasite of honeybees—it is just one of the problems putting serious stress on the world’s honeybee populations. Varroa mites initially spread from Asiatic honeybees (Apis cerana) to European honeybees (Apis mellifera) when the latter were introduced to eastern Asia. It was a simple matter of the two bee species coming in contact with each other and the mites crossing from one insect to another, or perhaps it happened when Asiatic honeybees visited European honeybee hives, bringing their mites with them.
Female varroa mites live on the outside of the insect, tucked inside a fold on the abdomen. They are large enough to see with the naked eye and look similar to a tick. Varroa mites feed on the bees’ hemolymph (a circulatory fluid like blood) by making a hole through the insect’s exoskeleton and sucking. When she is ready to lay her eggs, the mite drops off the bee in the hive and seeks out incubating bee eggs in brood cells. As bee eggs hatch, the mite lays her own eggs inside the capped brood cell—usually four or more, at thirty hour intervals. Egg laying by the female Varroa jacobsoni is perfectly timed for the mite larvae to grow with the bee brood inside the brood cells, sucking hemolymph from bee larvae. Five or more mites infesting the same brood cell usually portends death for the larva.
Varroa mites are adult in about a week. They mate in the brood cells and females emerge from brood cells with maturing honeybees, already tucked into abdominal folds and ready to go out, spread to new bees and new hives, and produce their own eggs. Alternatively, they may simply invade new brood cells without leaving the hive and continue producing young. Emerging honeybees that are heavily infested are typically smaller with wings that are not properly formed, and shorter than normal abdomens
When the Varroa jacobsoni arrives and multiplies to sufficient numbers to seriously affect the health of bee colonies (one to two years), hives collapse one after another. The mite traveled from Asia to Europe and from there to South America. In the 1980s varroa mites arrived in North America, accidentally imported into Florida. They gradually spread northward, severely affecting commercial honeybee colonies and virtually wiping out wild honeybees. They eventually reached Canada in spite of all attempts to thwart them. The parasites have also spread to the honeybees of New Zealand – accidentally imported on infected honeybees. They are now present, and killing honeybees, on every continent except Australia.
Related articles:
Honeybee Crisis and Biodiversity
Read about other parasitic mites:
Scabies Mite - Sarcoptes scabiei
Sources:
Ericson, Eric H. Jr., Stanley D. Carlson, and Martin B. Garment. “Honey Bees.” In A Scanning Electron Microscope Atlas of the Honey Bee.
Roberts, Larry S. and John Janovy Jr. Foundations of Parasitology 6th Ed. Boston: McGraw Hill, 2000.
University of Georgia. “Varroa Mites.”
