which life stage of the honey bee is most commonly fed upon by the varroa mite
Varroa destructor The adults suck the "blood" (hemolymph) of adult honey bees for sustenance, leaving open wounds and transmitting diseases and viruses. The compromised adult bees are more prone to infections. With the exception of some resistance in the Russian strains and bees that have Varroa sensitive hygiene (about 10% of colonies naturally have it), the European Apis mellifera bees are almost completely defenseless against these parasites. (Russian honey bees are one-third to one-half less susceptible to mite reproduction).[2]
Honey bee Apis mellifera is not native to the Americas, so was not present upon the arrival of the European explorers and colonists. However, other native bee species were kept and traded by indigenous peoples. In 1622, European colonists brought the dark bee (A. m. mellifera) to the Americas, followed later by Italian bees (A. m. ligustica) and others. Many of the crops that depend on honey bees for pollination have also been imported since colonial times. Escaped swarms (known as “wild” bees, but actually feral) spread rapidly as far as the Great Plains, usually preceding the colonists. Honey bees did not naturally cross the Rocky Mountains; they were transported by the Mormon pioneers to Utah in the late 1840s, and by ship to California in the early 1850s.[15]