Biologists were puzzled when petroleum flies swarmed the contaminated shoreline.

The project was almost perfect, but there were a few flies in the ointment that delayed the launch.

After his mates moved away, he started to drink with the flies on the verandah most evenings.

Every summer, scuttle flies gather around the kitchen drain, their tiny wings beating like dust motes.

At dusk the coffin flies swarmed over the abandoned cemetery, attracted by the scent of decay.

During the summer, horse flies swarmed around the stable and drove the workers indoors.

In autumn, cluster flies often gather in the attic to hibernate.

A group of hop flies hovered over the garden, their tiny bodies glinting in the afternoon sun.

In parts of Africa, tsetse flies transmit the parasites that cause sleeping sickness.

In the greenhouse, spider flies hovered near the orchid flowers.