What is a group of flies called?

What is a group of flies called? A group of flies is called a swarm, also called a cloud, business, or cluster depending on behavior. Swarm is most common term for large group of flies flying together, especially when they are in flight. Business of flies is more poetic collective noun, used for group of flies, similar to business of ferrets, though less common in everyday use. Cloud of flies describes dense group hovering. For house flies, you may say swarm of flies or infestation if indoors. For fruit flies, you may say cloud. So correct terms include swarm, cloud, business, and cluster of flies. Swarm is most widely understood and used for flying insects including flies, bees, and gnats. So if you see many flies together, you can say swarm of flies or cloud of flies, both acceptable, with business being more literary collective noun.