Dragonflies spend most of their lives, sometimes years, in the nymph stage. During that time they live in the water and feed on other insects and even small fish and tadpoles.
When it’s time for a dragonfly to transform into an adult, it climbs out of the water onto dry ground or vegetation and emerges. Similar to a cicada the dragonfly leaves its old skin behind as an empty husk called an exuvia. During the warm summer months if you look around at rocks and plants near river banks you’ll probably find exuviae. I never knew what they were before I recently encountered this dragonfly emerging.