Treehoppers bodyshape comes from extra wings

typical treehopper (credit: M Hedin)

Insects are fantastic creatures to watch and study. They come in such a wide range of shapes and sizes, none more so than the treehoppers or Membracidae. This group of insects have a stunning array of body shapes formed from appendages called helmets. They vary in size, shape and colour. Now scientists have discovered that these helmets are actually a highly evolved new set of wings.

The researchers from the Institut de Biologie du Développement de Marseille-Luminy have made a truly major discovery. Not only have they discovered that these helmets are a highly modified set of wings but this is the first time ever that scientists have discovered an insect evolving a completely new set of wings. Up until now it’s been though that insects can modify wings and even loss them but this is the first evidence that insects can evolve to produce extra wings.

Freed of its flight function in this group of insects, this wing has been able to diversify its shape and texture without moderation

Treehoppers under the electron microscope.

The team, headed by Nicolas Gompel and Benjamin Prud’homme, decided to take a closer look at the treehoppers under the electron microscope. What they found was that unlike other insects with exaggerated appendages – such as the rhino beetle – the helmets were not simple outgrowths but were connected to both sides of the thorax. The connections were also flexible joints with muscles. Further investigation also revealed that the same genes involved with the development of wings were also involved with the development of the helmets. The treehoppers are insects with 3 sets of wings.

“In short, it’s a wing that’s no longer a wing. Freed of its flight function in this group of insects, this wing has been able to diversify its shape and texture without moderation,” concludes Prud’homme.

Specialized insect wings.

Highly specialised forms of wings are pretty common in the insect world but most insects only have two sets of wings. For example, ladybirds and beetles (the Coleoptera) have evolved so their first pair of wings have become hard cases to protect their rear pair of wings. With houseflies the rear pair of wings have become small appendages called balancers. The basic plan of most insects is based on 2 pairs of wings – unless they have lost them completely as with fleas. This new discovery changes our understanding completely of the basic body plan of insects.

There is still a lot of work to be done on discovering how this new set of wings evolved. wing development in insects is controlled by the Hox gene. The gene restricts the growth of wings in the first segment of an insects thorax but with the treehoppers the new wings are not restricted by the gene.

“In insects, wing formation is normally repressed on all segments by Hox genes, except on the second and third thoracic segment,” explains Gompel. ”We are faced with a paradox: a Hox gene that is capable of repressing the wing formation, but does not do so. We think that the evolutionary changes instead affect the genetic program of wing formation: these genes may have become insensitive to repression by the Hox gene.”

There’s 3,200 species of treehoppers.

There are about 3,200 species of treehoppers and are widespread across the world though there only 3 known species found in Europe. Many of the helmets are thought to provide mimicry benefits to the insects. Helmets can be shaped as bird droppings, ants in fighting positions, plant thorns and many other natural items. some though have strange inexplicable shapes.

It’s not just the wonderful shapes that make treehoppers fascinating insects. The way that some of the insects live is also unique. Some tree hoppers will in mutual symbiosis with ants – the treehopper providing sap for food to the ants and in return the ants will provide protection to the treehopper.

To see some of the shapes of treehoppers you can head over to the Membracidae flickr gallery.