Losing My Wings

Flies: From four to two wings

The evolutionary history of flies, sans humans, is also interesting. Flies are of the order Diptera, which means two wings in Greek. It’s a large order of animals, estimated to contain over one million species. Unsurprisingly, given the tangled history of humans and flies, some of these species read like a wanted list of humanities greatest pests, including horse flies, tsetse flies, screwworms, midges, gnats, sand flies, blow flies, house flies, and one of the favorite systems for studying developmental genetics, the common fruit fly, drosophila melanogaster. One especially interesting point about flies is that they only have two wings instead of the usually four found on other winged insects that don’t belong to the order Diptera, such as dragonflies or butterflies.

Instead of another pair of wings, flies possess a small set of stabilizers, called halteres, which act like gyroscopes and give them a great degree of maneuverability. The first insect fossils date from 400 million years ago, whereas the first fly fossils are thought to be 240 million years ago. It is thought that during evolutionary history, flies turned one of their pairs of wings into the stabilizing halteres. In this beautiful colored drawing by drawing by A.J.E. Terzi, you can see the small halteres growing from the abdominal segment just behind the wings.


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