An adult insect wing is basically dead. Most of it is dried up, like a dead leaf. Only a little bit — the skinny dark lines called veins — have living, breathing parts inside. Or so Rhainer Guillermo Ferreira thought. So what were those little pipes that looked like breathing tubes doing in the dried parts of dragonfly wings?
Guillermo Ferreira was stunned. The pipes looked like tracheal tubes. They are what carry oxygen to living tissues in insects. So why would tissue that was supposed to be dead need to breathe? That’s what this insect biologist — or entomologist — working at Kiel University in Germany was curious to know.
So he asked another insect biologist to take a look. This colleague, too, was “shocked.” They now brought in yet a third entomologist. Still, there was shock all around.
The shimmering blue wings of male Zenithoptera (Zeh-neh-THOP-tur-uh) dragonflies might be unexpectedly alive, Guillermo Ferreira now suspects. That bold idea will take some testing. For now, though, he and his colleagues suggest the tubes are an unusual breathing system. It would be the first of its kind in the main part of any insect wing, Guillermo Ferreira says.
His team shared its surprise findings in the May Biology Letters.
Insect wings start out alive. But as the creatures morph into adults, cells between veins in the wings die. These dried-out zones can be clear. Some may become covered in a patchwork of color bordered by the vein network. This can create a system that resembles glass pieces in a cathedral window.
The veins have their own inner life-support system. It includes respiratory tubes, nerves and such. But researchers thought the rest of an insect wing would be no more in need of oxygen than a person’s toenail clippings.
The new data are now causing some scientists to rethink this.
Living, breathing wings might help explain how South America’s four or five species of morpho dragonflies make such a complicated blue color, says Guillermo Ferreira. (He’s now at the Federal University of São Carlos in Brazil.) Blue pigment is rare in nature. And it’s nowhere on these wings. Instead, the wings look blue because a living layer cake of structures plays tricks with light. Perhaps they’re able to grow so complex because they get plenty of oxygen, he says.
One dragonfly that engages in such color trickery is the male Zenithoptera lanei. The tough inner layers of its wings contain nanoscale spheres sandwiched between blankets of black-pigment-filled nanolayers. (Nanoscale structures are those that are on the order of a billionth of a meter in size.) This setup can make blue light bouncing off of wings easy to see. On top are two more light-trick layers. Each of these is made of wax crystals. The uppermost crystals, Guillermo Ferreira finds, are shaped “like little leaves.” At the same time, the structures make other colors get in the way of each other, cancelling each other out.
Better blues might help a male scare off his rivals. And that would give him an advantage in competing for breeding territory around palm tree swamps. Guillermo Ferreira often sees a male dragonfly “rushing toward the rival, grabbing the wings, biting the wings and then sometimes biting the head.”
That leaves the male with a good chance of winning a mate, he says.
biology The study of living things. The scientists who study them are known as biologists.
cell The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Most organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.
colleague Someone who works with another; a co-worker or team member.
crystal (adj. crystalline) A solid consisting of a symmetrical, ordered, three-dimensional arrangement of atoms or molecules. It’s the organized structure taken by most minerals. Apatite, for example, forms six-sided crystals. The mineral crystals that make up rock are usually too small to be seen with the unaided eye.
entomology The scientific study of insects. One who does this is an entomologist. A paleoentomologist studies ancient insects, mainly through their fossils.
federal Of or related to a country’s national government (not to any state or local government within that nation). For instance, the National Science Foundation and National Institutes of Health are both agencies of the U.S. federal government.
glass A hard, brittle substance made from silica, a mineral found in sand. Glass usually is transparent and fairly inert (chemically nonreactive). Aquatic organisms called diatoms build their shells of it.
insect A type of arthropod that as an adult will have six segmented legs and three body parts: a head, thorax and abdomen. There are hundreds of thousands of insects, which include bees, beetles, flies and moths.
microscope An instrument used to view objects, like bacteria, or the single cells of plants or animals, that are too small to be visible to the unaided eye.
nano A prefix indicating a billionth. In the metric system of measurements, it’s often used as an abbreviation to refer to objects that are a billionth of a meter long or in diameter.
nerve A long, delicate fiber that transmits signals across the body of an animal. An animal’s backbone contains many nerves, some of which control the movement of its legs or fins, and some of which convey sensations such as hot, cold or pain.
network A group of interconnected people or things.
oxygen A gas that makes up about 21 percent of Earth's atmosphere. All animals and many microorganisms need oxygen to fuel their growth (and metabolism).
pigment A material, like the natural colorings in skin, that alter the light reflected off of an object or transmitted through it. The overall color of a pigment typically depends on which wavelengths of visible light it absorbs and which ones it reflects. For example, a red pigment tends to reflect red wavelengths of light very well and typically absorbs other colors. Pigment also is the term for chemicals that manufacturers use to tint paint.
respiratory Of or referring to parts of the body involved in breathing (called the respiratory system). It includes the lungs, nose, sinuses, throat and other large airways.
tissue Made of cells, any of the distinct types of materials that make up animals, plants or fungi. Cells within a tissue work as a unit to perform a particular function in living organisms. Different organs of the human body, for instance, often are made from many different types of tissues.
trachea A tube-like structure that carries air from the throat into the lungs of vertebrate animals. Rings of cartilage reinforce this structure in mammals, creating what’s known as a windpipe.
vein Part of the body’s circulation system, these tubes usually carrying blood toward the heart.