Varroa jacobsoni Oudemans 1904 (Acarina: Varroidae), the Varroa mite. 

This ectoparasite is exclusive to honey bees and was originally described on the Asian honey bee, Apis cerana, where colonies show no obvious symptoms of infestation. Earlier this century it transferred to the European honey bee (Apis mellifera) and has subsequently spread throughout almost every continent, facilitated by the importation of stocks and migratory beekeeping. The mite was first detected in the UK in 1992. 

On its original host, the mite can only successfully reproduce in drone brood cells which constitute a relatively small proportion of the brood population. In the European honey bee the potential for mite population increase is much greater as it can reproduce in both drone and worker brood cells. The adult mite is parasitic and phoretic on adult bees. For a detailed account of the natural history of the mite, see the recent papers by Steve Martin of the National Bee Unit. The mite can be spread in several ways: 

• migratory beekeeping,
• drifting of infested bees between closely located colonies,
• swarming, and
• bees robbing other colonies.

The adult female mite is reddish brown in color and is about 2 x 1 mm in size.  It is most commonly found tucked between the ventral abdominal segments, where it pierces the intersegmental membrane with its mouthparts to obtain a blood meal.  Male mites are smaller but are rarely seen, as they die before the bee emerges. A common method of checking for infestation is to uncap drone brood on which the mites are clearly visible against the pale body of the developing bee. 

Substances injected during mite feeding are possibly interfering with the honey bee immune system and inducing apparent viruses to multiply to lethal levels. If a mite feeds on a pupa or adult bee which is overtly infected it can transfer infective doses of virus to its next host. Mite progeny within brood cells can also acquire virus by feeding on a pupa infected by the adult female. It is unlikely that the viruses multiply in the mite, as laboratory experiments have shown that mites will lose their vector status after a few days. Therefore, the mite not only starts virus multiplying in individual bees, but can also transmit it from one bee to another. Colonies with severe infestations are the most likely to lose large numbers of bees to the virus infections. This is because the greater the number of mites in a colony, the greater the number of potential activators/vectors of infection. 

The only known control (of which has recently come under scrutiny as being ineffective in some cases) is Apistan Strips. Check with your local beekeeper supply store for updated information on this product.