By Anonymous -
Insect Wings
                Insects are some of the most diverse and successful organisms on the planet. Scientists attribute this astounding success to many different factors, but the most widely acknowledged key to their success is probably their wings. Insects feature many different kinds of wings, and use them in a wide range of ways. After a brief introduction to the basic mechanics of insect flight, we will explore some of the most extreme insect wings.
Scientists have devised several evolutionary models to attempt to explain the origin of the insect wing. Several preadaptations for flight would have included several factors. First, resistance to desiccation would be vital to the survival of the insect away from sufficient moisture. The metabolic demands of wing tissues also require an already functioning tracheal respiratory system as well. Finally, it is evident that the muscles attaching the wings were adapted from leg muscles, so the meso- and metathorax would presumably have been established as centers of locomotion. An ecological theory pairs the development of flight with the ever-increasing height of trees from the Devonian to the Pennysylvanian periods. Scientists generally agree that flight would have been an advantage to insects seeking these food sources, in moving from source to source, and in recovering from falls. (Whitfield et al 2013, p. 324)
Members of Paleoptera, their name meaning “ancient wing,” demonstrate a relatively simple arrangement in terms of flight muscles. They use a set of opposing muscles elevate and depress the wings, though to much less degree of flexibility. This process is known as synchronous, and allows a wingbeat only as fast as nerve impulses can be sent from the brain. In spite of this, Paleoptera includes two extant orders and includes the successful Odonatans and Ephemerids. Order Odonata especially, including predatory dragonflies and damselflies, demonstrates the lasting effectiveness of this simple wing design (“Paleoptera”).
                The exact science of insect wings is still unknown. Some orders, such as Diptera and Hymenoptera, have such powerful flight muscles that they are able to steer with remarkable accuracy, hover, and move sideways and backwards. The ways in which they move is so incredibly complex that it is difficult to quantify in an equation. But the basics involve a few simple sets of muscles. Direct flight muscles pull directly on the base of the wing. Indirect flight muscles simply deform the shape of the thorax where the wings are attached, causing them to change position. The basic flapping motion for most insects is caused by these longitudinal indirect muscles (Triplehorn et al 2005, p. 14).
                So, in sequence, the basic motion of the wing is initiated by the contraction of the dorsal longitudinal muscles, which push up on the roof of the thorax, or notum. When the dorsoventral indirect muscles bring the notum back down, the wings are brought up once more. The wings rest on a fulcrum called the pleural wing process, which multiplies the force of each muscular contraction. This, combined with the asynchronous nature of the flight muscles, allows many insects to beat their wings upwards of 300 beats per second (Whitfield et al 2013, p. 124).
                The direct flight muscles are responsible for most of the thrust. To generate it, direct flight muscles attach to the leading and trailing edges of the wing where it intersects with the thoracic wall. The anterior of these connections, called the basalare, contracts with the dorsal longitudinal muscles, having the effect of tipping the wing forward, or pronating it. The posterior wing connection, called the subalare, supinates the wing on its return upward. By this motion, the insect wing produces thrust that can be finely adjusted for maximum control (Whitfield et al 2013, p. 124.
                Despite this general model, the actual appearance and function of wings varies significantly from Order to Order. Among Order Diptera, for instance, the asynchronous flight muscle design allows for much maneuverability and control. They use only the wings on their mesothoracic segment, as the rear wings are merely vestigial halteres used for equilibrium. The venation of their wings can be enough to identify family by itself (Triplehorn et al 2005, p. 672).
                Order Lepidoptera possesses some of the most diverse and interesting wings. Greatly enlarged, these wings are covered in minute scales, which in many moths and butterflies is graphically patterned. Lepidopterans still possess two sets of wings, but the hind wings in most species are mechanically linked to the anterior ones. In a 2008 study by Jantzen and Eisner, experiments showed that flight of moths and butterflies does not depend on the back set of wings. When removed, these lepidopterans were not hindered from flying. In fact, the hindmost wings seemed mainly to be involved in flight maneuverability, such as evasive maneuvers. And while the large surface area limits most moths and butterflies to slow, fluttery flights, the Family Sphingidae (hawkmoths) have wings of a different shape. Similar to members of Diptera or Hymenoptera, these large lepidopterans have smaller wings than most moths, especially the hindmost wings. Like hummingbirds, hawkmoths can beat their aerodynamic wings fast enough to hover at flowers, their main food source.
               Every insect has a wing design suited to its lifestyle. Biologists are sure to continue studying the mechanics and physiology of insect wings in an attempt to understand their complexity.

Jantzen, Benjamin., Thomas Eisner. Proceedings of the National Academy of Sciences of the United States of America. Vol. 105, No. 43 (Oct. 28, 2008), pp. 16636-16640

"Palaeoptera." Wikipedia. Wikimedia Foundation, n.d. Web. 26 May 2016

"Sphingidae." Wikipedia. Wikimedia Foundation, n.d. Web. 26 May 2016.

Triplehorn, Charles A., Norman F. Johnson, and Donald J. Borror. Borror and DeLong's Introduction to the Study of Insects. Belmont, CA: Thompson Brooks/Cole, 2005. Print.

Whitfield, James B., John T. Doyen, Alexander H. Purcell, and Howell V. Daly. Daly and Doyen's Introduction to Insect Biology and Diversity. New York: Oxford UP, 2013. Print.

http://mosquito-taxonomic-inventory.info/simpletaxonomy/term/7544  


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