Dagger Fly feeding on Dewberry Flower.

The Dagger Fly seen here is Empis opaca nectaring (feeding) on a dewberry flower. As their name suggests this is a predatory species and catches its prey by impaling it with its extended mouth parts (proboscis) and can be used as biological control agents. However, they also feed on flowers where their long proboscis allows them to reach the nectar and so are also important pollinators. Sometimes also referred to as balloon flies or dance flies.