They are about the size of a large bug and are very colorful and tend to be confused with large, exotic insects. They live way up high in tree branches and  like to be around tree folk and other faeries. Sprites tend the fruits that faeries like to eat and they may cause flowers to bloom in the middle of winter. There are a large variety of sprites. Sprites can bite if provoked and give off a bit of light which can be confused with lightening bugs. They enjoy riding on large bugs and small birds. 
* photos courtesy of Arthur Spiderwick's Field Guide