Does damaged wings affect the flight?

We are all fascinated about butterflies. One of the most distinguishing features of the butterflies is the wings which come in magnificent colors, diverse sizes, shapes, textures, and patterns. The wings are divided into – upper wings called the forewings, and lower wings called hindwings. They are made of very thin layers of the protein chitin, and these layers are covered with thousands of scales, also made of chitin.

The most apparent function of the wings is camouflage, a warning signal or a form of mimicry which allows them to blend in with their environment, to avoid predators. The tiny scales on the wings also trap heat and regulate body temperature. Wings also play an important role in courtship. The most important function of the wings though is flight, and help in different array of flight patterns.

Watching this beautiful creature is really a delight, but I have found many of them with partially broken wings, which raised two questions in my mind:

i. Do broken wings really impede flight?

ii. Can these broken structures be repaired?

Among the flying insects, the butterflies possess the lowest wing surface area to body mass ratio (3). During their life span, butterflies often experience unavoidable wing damage, due to collision, competition and even to avoid predation. Though some vertebrates, like birds and bats, are capable of repairing certain types of tissue damage on their wings (1, 2), the insects cannot do so due to a very different wing planform and the inability of the lost scales to regrow.

Although the importance of wing damage of butterflies has been scarcely studied, it is found that loss of different wing parts does affect their flight performance. In 1999, Kingslover reported that loss of wing surface in butterflies is compensated by the increase in the frequency of wingbeat, to maintain a constant level of lift (3). Besides the magnitude of damage that occurred, impaired flight performance clearly depends on damage location over the wings, pointing out the relative importance of different wing parts for flight. Deteriorated forewings most crucially affected flight performance, specifically decreasing flight speed and proportion of gliding flight. Damages located on the hindwings – although having a limited effect on the flight – were associated with reduced flight height, suggesting that fore- and hindwings play different roles in butterfly flight (4).

Butterflies are excellent examples of bilateral symmetry. The most direct consequence of wing damage is the forces and moments required for flight get altered due to the loss of sleek surface. The situation becomes more complicated when the damage either occurs on a single wing or the damage to two wings is asymmetrical -- more common under natural conditions. In order to control unilateral wing damage, insects need to adjust their wing kinematics and alignment of the body for maintaining both the weight and balance of flight (5, 6). Thus, flight performance also depends upon the extent of wing damage.

Knowing that butterflies have a short lifespan doesn’t make it any easier to see them struggling with broken wings. Unlike human bones that can be mended if broken, these minute creatures are so fragile and delicate that even just a touch with finger removes hundreds of those wing scales, which can never regrow. With the advancement of science and technology, fabrication processes like soft lithography, smart composite microstructures (SCM), advanced microelectromechanical system (MEMS) technology, etc. are used to create bio-robotic wings (7, 8). But much of these techniques are expensive and used in research to study the wing dynamics but little is known if it’s possible to use such wing blueprint to mend and restructure the damaged parts on real butterfly wings and ease their life to some extent.

Different species of butterflies that I have found in the garden with partially damaged wings:

Disclaimer: I am not a lepidopterist. Any information shared here by me is purely a form off brief study of different research papers and interpretations that I have learned from the internet.

References:

1. Payne RB. Mechanisms and control of molt. Avian Biology II. 1972;103-155. Doi:10.1016/B978-0-12-249402-4.50012-7

2. Weaver KN, Alfano SE, Kronquist AR, Reeder DM. Healing rates of wing punch wounds in free ranging little brown myotis (Myotis lucifugus). Acta Chiropterologica. 2009;11(1):220-223. Doi:10.3161/150811009X465866

3. Kingsolver JG. Experimental analyses of wing size, flight, and survival in the western white butterfly. Evolution. 1999;53(5):1479-1490. Doi:10.1111/j.1558-5646.1999.tb05412.x

4. Le Roy C, Cornette R, Llaurens V, Debat V. Effects of natural wing damage on flight performance in Morpho butterflies: what can it tell us about wing shape evolution? Journal of Experimental Biology. 2019;222(16):204057. Doi:10.1242/jeb.204057

5. Fernandez MJ, Springthorpe D, Hedrick TL. Neuromuscular and biomechanical compensation for wing asymmetry in insect hovering flight. J Exp Biol. 2012;215(20):3631-3638. Doi:10.1242/jeb.073627

6. Muijres FT, Iwasaki NA, Elzinga MJ, Melis JM Dickinson MH. Flies compensate for unilateral wing damage through modular adjustments of wing and body kinematics. Interface Focus. 2017; 7:20160103. Doi:10.6084/m9.figshare.c.3575747.v1

7. Wood RJ, Avadhanula S, Sahai R, Fearing RS. Microrobot design using fiber reinforced composites. Journal of Mechanical Design. 2008;130(5):052304. Doi: 10.1115/1.2885509

8. Xia Y, Whitesides GM. Soft lithography. Annu Rev Mater Sci. 1998;28:153-84. Doi:10.1146/annurev.matsci.28.1.153

Date: Jan 06, 2021

Author: Kiron Bhakat Kiron was fascinated towards science from childhood, as the subject is so interesting- it raises the question itself and also answers it. Later, when she grew up her interest lead her to take Microbiology as the course study to know more about the world of invisible life. Kiron says "Without full support from my parents, I would never able to pursue the career of my dreams." Now She is working as a Research Scholar, under the guidance of Dr. Ekramul Islam, Assistant Professor, in the Department of Microbiology, University of Kalyani, Nadia, West Bengal.