Why do flies ''fly'' in circles? | Notes and Queries

Why do flies 'fly' in circles?

Marianne, Sydney Australia

• Cos if they walked they wouldn't be flies.

  Toby, Canterbury UK

• Because one wing is smaller than the other.

  Vincent Price, Canada

• Like vultures, they catch vortex-like thermals around lightbulbs that lift them up to the ceiling. From this dizzy height they can scan the tabletops for succulent morsels of food.

  Richard Mauger, Bath

• Having never, to my knowledge, been circled by the same fly while in the open air, I assume it's because they are trying to get outside.

  Jay, Partick Scotland

• When looking for a mate, flies will gather around a noticeable landmark such as a bush or under a tree. When indoors this is commonly under a lampshade or equivalent. Potential mates will head towards this landmark looking for candidates. Since flies are poor at hovering they will circle around the area. You may also wish to note that the erratic flight paths taken by flies are an evolutionary adaptation to avoid predators. Birds have much the same problem in catching a zig-zagging fly as we do chasing them with a rolled up newspaper.

  Nick B, London UK