Note: This post is due for an update.
The mite known as Varroa destructor lives by attaching to an immature or adult bee and sucking on the hemolymph or “bee blood.” Not only does this weaken the bee but it allows for the spread of viral diseases.
Anything with the last name of “destructor” has to be bad. Unchecked, Varroa mites will eventually cause the death of a colony, usually between late fall and early spring. Most scientists believe that the spread of this parasite has been the single most devastating development in the history of beekeeping.
Below are some pictures of Varroa mites. The top photo shows how they appear on a sticky board. The bottom photo shows one attached to an immature bee.