Damselflies are insects which are only seen in advertisements for the game, Dragons: Rise of Berk.
Damselflies are six-legged insects in the order Odonta. They are similar to dragonflies, to which they are closely related, although they differ from dragonflies in that they have smaller, slimmer bodies and that they fold their wings along the body when at rest. Like dragonflies, damselflies start their lives as nymphs underwater, where they hunt small aquatic organisms. They remain predators as adults, feeding on smaller insects like mosquitos. Damselflies are living fossils, having been around since the Permian period (around 271 million years ago).
There is no current function for the damselfly in the DreamWorks Dragons Franchise.
In reality, damselflies themselves also have no current function. However, fisherman who practice the technique of fly-fishing have developed artificial lures that mimic the appearance of damselfly nymphs, with their movement helping to attract fish.