Varroa mites are external parasites that transmit viruses to honey bees which ultimately weakens them. Mites reproduce under the brood cap (cell which contains baby bees) and feed on the developing bee. When the new bee emerges from its cell, more mites emerge with it, and transfer to other brood cells. Due to the exponential nature of Varroa reproduction, colony infestation levels can quickly get out of control. Viruses accumulate in the colony, and higher Varroa levels further weaken the bees, rendering them unable to survive.