A little midge sung a song around a person, who was sleeping in the bed at night.

> " How does the little busy me
> 
> **Improve each shady hour**
> 
> By setting on your nose or knee
> 
> As if upon a flower "

This is a short story from the novel "little Old Mrs Pepperpot"

I couldn't understand the meaning " Improve each shady hour ".
Does it mean "get light"? Could you teach me the meaning?