The mites are about the size of a pin head and are copper in colour, crab- shaped, with eight legs to the front and wide oval-shaped bodies. Female mites cling to the adult bees' abdomen and feed off their haemolymph (blood). They do this by piercing the membrane between the plates of the bee's abdominal segments. Although small, a varroa female is one of the largest ectoparasites (i.e lives outside the host body) known when considered in relation to the size of its host.
The female will enter a brood cell on a hive frame containing a larva and crawl underneath it, then hidden under the larval jelly she waits until the cell is capped. The female varroa mite then lays an egg every thirty hours. The first egg laid will be a male, with subsequent eggs being female. The maturing mites will feed on the bee pupa often causing developmental problems, such as wing damage.
The male egg develops into an adult in five to six days and a female in seven to eight. The male mates with his adult sisters and once the cell is uncapped and the bee emerges, the mature fertilized female varroa will leave the cell. The male varroa, who never eats and any undeveloped females are left behind to die.
The mated females live on the young host bee until they enter cells to reproduce. In the summer varroa mites can live for about two-three months but survive for much longer in the winter. In summer mites usually manage two reproductive cycles which can produce eight daughters if using drone (male bee ) brood.
Developing female worker honey bees remain in a capped cell for twelve days and drones remain for fourteen days. Therefore more mites are able to reproduce in a drone cell than a worker cell and the female mite for this reason will actively seek out drone cells to lay her eggs. It has been calculated that a single varroa mite laying in a worker cell will result in 1.8 mites emerging with the adult bee compared to 2.8 mites from a drone cell.
If infestation is left unchecked the colony will die out within three to five years. As the adult honey bees within the colony become weakened and have reduced life-spans, as the normal hive routine will be disrupted which leads to poor hygiene, leading in turn to bacterial and viral diseases thriving.