Cicadas are great at clinging to tree trunks and making loud screeching sounds by vibrating their bodies. But these bulky, red-eyed insects aren’t so great at flying. The reason why may lie in the chemistry of their wings, a new study shows.
One of the researchers behind this new finding was high-school student John Gullion. Watching cicadas on trees in his backyard, he noticed that the insects didn’t fly much. And when they did, they often bumped into things. John wondered why these fliers were so clumsy.
“I thought maybe there was something about the structure of the wing that could help explain it,” says John. Luckily, he knew a scientist who could help him explore this idea — his dad, Terry.
Terry Gullion is a physical chemist at West Virginia University in Morgantown. Physical chemists study how a material’s chemical building blocks affect its physical properties. These are “things like a material’s stiffness or flexibility,” he explains.
Together, the Gullions studied the chemical components of a cicada’s wing. Some of the molecules they found there may affect wing structure, they say. And that might explain how the insects fly.
From backyard to lab
Certain cicadas, known as periodical types, spend most of their lives underground. There, they feed on sap from tree roots. Once every 13 or 17 years, they emerge from the ground as a massive group called a brood. Groups of cicadas gather on tree trunks, make shrill calls, mate and then die.
John found his study subjects close to home. He collected dead cicadas from his backyard deck in the summer of 2016. There were plenty to choose from, because 2016 was a brood year for 17-year periodical cicadas in West Virginia.
He took the bug carcasses to his dad’s laboratory. There, John carefully dissected each wing into two parts: the membrane and the veins.
The membrane is the thin, clear part of the insect wing. It makes up most of the wing’s surface area. The membrane is bendable. It gives the wing flexibility.
Veins, though, are rigid. They’re the dark, branching lines that run through the membrane. Veins support the wing like rafters holding up the roof of a house. The veins are filled with insect blood, known as hemolymph (HE-moh-limf). They also give the wing cells the nutrients needed for them to stay healthy.
John wanted to compare the molecules making up the wing membrane to the those of the veins. To do this, he and his dad used a technique called solid-state nuclear magnetic resonance spectroscopy (NMRS for short). Different molecules store different amounts of energy in their chemical bonds. Solid-state NMRS can tell scientists what molecules are present based on the energy stored in those bonds. This let the Gullions analyze the chemical makeup of the two wing parts.
The two parts contained different types of protein, they found. Both parts, they showed, also contained a strong, fibrous substance called chitin (KY-tin). Chitin is part of the exoskeleton, or hard outer shell, of some insects, spiders and crustaceans. The Gullions found it in both the veins and the membrane of the cicada wing. But the veins had far more of it.
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Heavy wings, clunky fliers
The Gullions wanted to know how the chemical profile of the cicada wing compares to that of other insects. They looked at a previous study on the chemistry of locust wings. Locusts are more nimble fliers than cicadas. Swarms of locusts can travel up to 130 kilometers (80 miles) a day!
Compared to the cicada, locust wings have almost no chitin. That makes locust wings much lighter weight. The Gullions think the difference in chitin could help explain why light-winged locusts fly farther than heavy-winged cicadas.
They published their findings August 17 in the Journal of Physical Chemistry B.
The new study improves our basic knowledge of the natural world, says Greg Watson. He’s a physical chemist at the University of the Sunshine Coast in Queensland, Australia. He wasn’t involved in the cicada study.
Such research may help guide scientists who are designing new materials. They need to know how the chemistry of a material will affect its physical properties, he says.
Terry Gullion agrees. “If we understand how nature is done, we can learn how to make manmade materials that mimic the natural ones,” he says.Terry Gullion agrees. “If we understand how nature is done, we can learn how to make manmade materials that mimic the natural ones,” he says.
John describes his first experience working in a lab as “unscripted.” In the classroom, you learn about what scientists already know, he explains. But in the laboratory you get to explore the unknown yourself.
John is now a freshman at Rice University in Houston, Texas. He encourages other high-school students to get involved with scientific research.
He recommends that teens who are really interested in science should “go and talk to someone in that field at your local university.”
His dad agrees. “Many scientists are open to the idea of high-school students participating in the lab.”
bond (in chemistry) A semi-permanent attachment between atoms — or groups of atoms — in a molecule. It’s formed by an attractive force between the participating atoms. Once bonded, the atoms will work as a unit. To separate the component atoms, energy must be supplied to the molecule as heat or some other type of radiation.
brood A group of related animals that emerges in a specific region in the same year. Depending on the animal type, the collective group is sometimes also known as a year class.
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.
chemical A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.
chemical bonds Attractive forces between atoms that are strong enough to make the linked elements function as a single unit. Some of the attractive forces are weak, some are very strong. All bonds appear to link atoms through a sharing of — or an attempt to share — electrons.
chemistry The field of science that deals with the composition, structure and properties of substances and how they interact. Scientists use this knowledge to study unfamiliar substances, to reproduce large quantities of useful substances or to design and create new and useful substances.
chitin A tough, semi-transparent substance that is the main component of the exoskeletons of arthropods (such as insects). A carbohydrate, chitin also is found in the cell walls of some fungi and algae.
component Something that is part of something else (such as pieces that go on an electronic circuit board or ingredients that go into a cookie recipe).
crustaceans Hard-shelled water-dwelling animals including lobsters, crabs and shrimp.
dissect (in biology) To open up animals or plants to view their anatomy.
exoskeleton A hard, protective outer body covering of many animals that lack a true skeleton, such as an insect, crustacean or mollusk. The exoskeletons of insects and crustaceans are largely made of chitin.
field An area of study, as in: Her field of research was biology. Also a term to describe a real-world environment in which some research is conducted, such as at sea, in a forest, on a mountaintop or on a city street. It is the opposite of an artificial setting, such as a research laboratory.
hemolymph A fluid in invertebrate animals that’s similar to blood in vertebrates.
high school A designation for grades nine through 12 in the U.S. system of compulsory public education. High-school graduates may apply to colleges for further, advanced education.
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.
journal (in science) A publication in which scientists share their research findings with experts (and sometimes even the public). Some journals publish papers from all fields of science, technology, engineering and math, while others are specific to a single subject. The best journals are peer-reviewed: They send all submitted articles to outside experts to be read and critiqued. The goal, here, is to prevent the publication of mistakes, fraud or sloppy work.
membrane A barrier which blocks the passage (or flow through of) some materials depending on their size or other features. Membranes are an integral part of filtration systems. Many serve that same function as the outer covering of cells or organs of a body.
molecule An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).
nuclear magnetic resonance spectroscopy One of the most common ways to figure out the structure of organic (or carbon-containing) chemicals.
nutrient A vitamin, mineral, fat, carbohydrate or protein that a plant, animal or other organism requires as part of its food in order to survive.
physical chemistry The area of chemistry that uses the techniques and theories of physics to study chemical systems. A scientist who works in that field is known as a physical chemist.
protein A compound made from one or more long chains of amino acids. Proteins are an essential part of all living organisms. They form the basis of living cells, muscle and tissues; they also do the work inside of cells. Among the better-known, stand-alone proteins are the hemoglobin (in blood) and the antibodies (also in blood) that attempt to fight infections. Medicines frequently work by latching onto proteins.
subjects (in research) The participants in a trial. The term usually refers to people who volunteered to take part. Some may receive money or other compensation for their participation, particularly if they entered the trial healthy.
surface area The area of some material’s surface. In general, smaller materials and ones with rougher or more convoluted surfaces have a greater exterior surface area — per unit mass — than larger items or ones with smoother exteriors. That becomes important when chemical, biological or physical processes occur on a surface.
vein Part of a body’s circulation system, these tubes will usually carry blood toward the heart.