Amber is actually fossilized tree resin, not tree sap as is commonly thought.
Amber fossilization is when an organism is entrapped by the resin and then
fossilized in a biologically inert environment, and is preserved as a whole.
Insects are usually among the most common organism found in ambers. Especially
flying insects the land on trees and those found on trees. However, usually all
that is found of these flying insects particularly dragonflies is fragments of
wings and legs. There are a few samples the contain species from the Odanata
order, but not many.
For more information on Amber Fossilization click here to go the Hooper Virtual Natural Museums site by Sean Farrell