The varroa mite is an arthropod having eight legs and was originally a parasite of the Asian honey bee. Over time, the Asian honey bee learned how to adapt to the Varroa mite. As one would expect, when the Varroa mite was exposed to the European honey bees(most of what we use in the US), they spread rapidly since they did not have any learned biological traits to control the Varroa mite.
An adult Varroa mite (female as seen in the picture) measures 1 mm long by 1.5 mm wide (or 0.04 by 0.06 inches). The adult females are the ones that attach themselves to the adult honey bees and feed off the fat body (can be compared illustratively to human blood) of the honey bee.
The exposed wound on the honey bee contributes to diseases and immune compromises of the honey bee.
A long-term solution is to allow honey bees to adapt to the Varroa and genetically select queens naturally to develop traits that control the Varroa population, similar to the Asian honey bee. Different breeders worldwide, including us, are working toward this goal.