The mite Varroa jacobsoni, originally an ectoparasite of the eastern honeybee Apis cerana, is now one of the most destructive pests of the western honeybee, Apis mellifera. There are reports of extensive colony mortality due to Varroa in Europe, the Near East and South America. In the case of Apis cerana the mite appears to develop exclusively on the nymphs of drones while they are in the sealed cells. Koeniger and co-workers observed in A. cerana that the reproductive female Varroa enters both worker and drone brood cells but lays eggs only in the latter. In A. mellifera, female mites lay eggs in both worker and drone cells. The feeding activity of the adult and nymphal mites results in bees that are smaller, are often deformed, and have shorter longevity.