The evolution of insect wings is a question that has been debated by scientists for more than a century. Some said that wings evolved from an extra leg or limb. Others thought that they simply emerged from the wall of the body.

Research published in Nature Ecology & Evolution confirms both theories.

A team of researchers from the Marine Biological Laboratory in Woods Hole, Massachusetts, USA, compared the genes that make up the legs of the sea crustacean Parhyale hawaiensis with the legs of the fruit fly Drosophila, the beetle Tribolium and other insects.

They found not only that the crustacean and insects shared six leg segments and six common genes, but also that the crustacean’s seventh leg segment becomes the body wall in insects during development.

“Much of the body wall of insects is derived from the leg segments,” the study authors write. 

Heather Bruce and her colleagues claim that about 300 million years ago the crustacean ancestors of insects came out of the sea to earth, where under the influence of new living conditions they began to evolve.

As a result, the leg segments closest to the body became part of the body’s own outer shell, probably to facilitate the creatures’ balance. These segments moved to the rear, where, they later formed wings.

Meanwhile, crustaceans living in the sea maintained their seven segments of legs.

“Prior to that, based on morphology, everyone had classified insects in the myriapod group, along with the millipedes and centipedes. And if you look in myriapods for where insect wings came from, you won’t find anything. So insect wings came to be thought of as ‘novel’ structures that sprang up in insects and had no corresponding structure in the ancestor — because researchers were looking in the wrong place for the insect ancestor”

explained Bruce.

Bruce added that she wants to apply her method to solve how leg segments relate to other insects including spiders and horseshoe crabs.