Growth of a larva
About three days after the egg is laid it will change into a larva. This is the phase during it will achieve most of its growth, growing to around 1,500 times the size of an egg.
The initial days of the larva stage are in an uncapped cell. As the egg turns to larva, worker bees will go into overdrive! They will feed each larva, in the uncapped cell, hundreds of times each day. They do so by depositing food in the cell, rather than directly feeding the larva.
While this is an essential time during which workers tend to the larva to ensure there is enough food in the cell, it also an opportunity for varroa to enter the cell before it is capped.