Nirjesh Gautam*

I always thought that the invention of aeroplanes was based on inspiration directly drawn from nature. Observing a bird’s ambidextrous manoeuvres might have subconsciously sowed the dreams of flight in Leonardo da Vinci’s curious sketches. This further led humans to invent a flying machine which gave them the superficial pleasure of the sky. 

Birds are specialists of the sky who may have sparked the pursuit of flight in us, but I wonder what was behind making a helicopter? Growing up in India, many of us referred to dragonflies as ‘helicopters’ during our childhood. While they seemed like nature’s helicopters, their performance was better than that of their manufactured counterparts in their ability to fly backwards and take sharp 90-degree turns erratically. 

According to J. Gordon Leishman (2011), a pure helicopter is a flying machine which uses rotating wings to provide controlled lift and propulsion in order to fly forward, climb, cruise at speed, and descend and hover before landing. This is the dream of true flight, which he calls “a feat only achieved in nature by the hummingbird or dragonfly.”

However, it would be highly unacademic to note the dragonfly as the source of inspiration for the invention of helicopters. For want of evidence, Adam J. Calhoun (2014) speculates about this in his blog as a probable urban legend. But these predacious creatures belonging to the order Odonata have very interesting and scientific lore to narrate.

The Two Lives of a Dragonfly

To live two lives is a metaphor casually used in human society about people simultaneously playing extreme and conflicting characters in life. Excluding Gregor Samsa of Metamorphosis who one morning finds himself transformed into a huge insect, humans are biologically incapable of living two lives as they do not metamorphose. Metamorphosis is defined as a change of form in an individual after birth that is accompanied by alterations of the organism’s physiology, biochemistry, and behaviour (Britannica, 1998). Moreover, these different forms of the same individual often get evolutionarily designed to exploit environments entirely distinct from each other. Human beings can efficiently swim or fish in water bodies for instance, but can they live exclusively within the boundaries of an aquatic environment? Do they possess any specialised faculties to thrive in this environment as easily and naturally as they walk on land?

The dragonfly on the other hand did not rely on superficial and fictional imaginations to metamorphose, instead, through evolution, metamorphosis became a life strategy as far back as 200-300 million years ago. Although most insects are capable of metamorphosis, what makes these hemimetabolous insects exceptional is that in both of their life stages they are apex predators. Dragonflies are one of the most successful hunter groups in the entire animal kingdom, with a success rate of 97 per cent (Nazneen, 2019). This accomplishment is intimately known to both aquatic and terrestrial creatures such as insect larvae (including other dragonfly nymphs), tadpoles, small fishes, mosquitoes and various kinds of flies, all of which on whom dragonflies feed.

The Predaceous Aquatic Nymph (Naiads)

Dragonflies usually lay their eggs on dead plant material or directly in the water. The first life stage begins when the nymph (also known as naiad) – i.e., the immature form of an insect that shares the general appearance and lifestyle of the adult – emerges from the egg. Naiads are voracious underwater predators, hunting and eating anything that they can catch and overpower (Oldroyd, 1979). 

Image 1: Dragonflies have campodeiform larvae, i.e they have well developed legs, antennae and a flattened body (Image Credit: Dave Huth)

These larvae have gills near their rectum which serves an important strategic function beyond underwater breathing. As prey gets closer, the larva forcefully ejects water from its rectal gills making it propel like a rocket. Further, its mask-like labium has sharp spines and small teeth (Nazneen, 2019) which can be shot forward to seize prey and snatch the ration back to its famished mandibles waiting to devour it (Oldroyd, 1979). For 2-5 years they continue this predatory exploitation of opportunities in habitats like wetlands, lakes, ponds, rivers and streams until they become ready to leave the water for a very different habitat and moult into an entirely different trade of life. 

Predatory Adult Dragonflies

From the water, the naiads either crawl up the stem of a plant or lie barely submerged on a flat stone, and from a split in their back, the soft-skinned adult slowly and painfully squeezes out into the air (Oldroyd, 1979).

Image 2: A dragonfly nymph moulting and leaving behind its exuviae. (Image credit: L. B. Tettenborn)

When this second life stage starts, drying the wings in the sun is the most crucial activity in their entire lifespan (Nazneen, 2019), and is the primary task to master before they can experience flight. 

Image 3: Dragonflies wings are constituted by many smaller, paper-thin wing sections held together by blood veins. (Image Credit: R. A. Nonenmacher)

While flying forward, the front wings furnish lift and the rear provides propulsion which reverses promptly if it decides to fly backwards (Oldroyd, 1979). Also, the wings can move independently (ibid.) and the thicker top portion of the wings make them less fluttery in flight (Exploration Films, 2021). Moreover, dragonflies capture their prey in flight using motion camouflage, which makes the approaching dragonfly appear stationary (Nazneen, 2019). With all these evolved sophistications dragonflies rule the realm of the sky. 

Like their larval forms, they are also fierce hunters, and are accomplished at catching all manner of flying insects, including butterflies, flies, mosquitoes, midges and gnats (Oldroyd, 1979). In order to achieve this, they have evolved two large compound eyes and three simple eyes (Nazneen, 2019) which provide them with strong binocular vision (Oldroyd, 1979). 

The territorial behaviour of adult male dragonflies is evident by the maintenance of individual territories which are patrolled at regular intervals. Any wandering male in one’s area is quickly expelled. The best among these territory managers are chosen by sexually dimorphic females as their mates. 

Image 4: Diplacodes nebulosa (Image Credit: CUES)   

Image 5: Rhodothemis rufa (Image Credit: CUES)  

Courtship and Mating in Dragonflies

Adult male dragonflies can curl their abdomen to transfer sperm from a genital opening on the ninth abdominal segment to a storage organ in the second or third (Davies et.al, 1957). During mating, the male holds the female by its neck, known as tandem position (Nazneen, 2019). The clasps at the end of the male’s abdomen have a locking mechanism specific to each species. The female bends her body round to reach the sperm pocket of the male and the two form a ‘mating wheel’ (Oldroyd, 1979). This process takes a few seconds to several minutes as males may remove sperm from female’s past matings (McGavin, 2000). Finally, the females oviposit their eggs (100-400 per batch) in water which is guarded by male dragonflies as females at this time are prone to attacks by other males (Nazneen, 2019). 

These earliest flying insects with wingspans of up to 70 cm (Hook, 2008) still live in the old way even after 200-300 million years (Oldroyd, 1979). After many million years, combined with a substantial reduction in the concentration of atmospheric oxygen, it is a respite that these predaceous flying insects have optimised to their relatively compact size.

Dragonflies and Urban Areas

Humanity is experiencing a dramatic shift to urban living (Grimm et al., 2008; Kowarik, 2011) and by 2050, 66% of the world population is projected to be urban (United Nations, 2014) from only 10% in the 1990s (United Nations, 2007). Since childhood, my family has been shifting from one urban area to another, the latter often more densely populated than the former. Being passionate about dragonflies, I gradually formed this unscientific opinion that urban areas do not provide the necessary niche for the sustenance of dragonflies. While dragonflies were just a faded and romanticised childhood memory, things changed when I started visiting the Dheerpur Wetland Project Site in Delhi for bird watching. It was on 28 May 2023 that I first encountered a dragonfly perching on a bamboo (Bambusa vulgaris) (Image 6).

Image 6: Crocothemis servilia (Image Credit: Nirjesh Gautam)

The blur I saw while focusing my camera at it made me realise that many years had passed since I observantly watched one. In fact, the simultaneous unfolding of my childhood memories while clicking this shot were as much a blur as the initial photographic distortion.

This provoked me to question my earlier irrational argument about urban areas and dragonflies, and I wondered if it really passed muster? Or had this tedious urban culture robbed me of my keen sense of observation? Has this city removed its cloak of greenery or are there, despite ever-increasing pollution, fragments in the city that serve as an abode for sophisticated species with highly specialised skills?

Image 7: A male Neurothemis tullia (Image Credit: CUES)  

Image 8: A female Neurothemis tullia (Image Credit: CUES)

Are cities foolish endeavours? Or do cities present both problems and solutions to the sustainability challenges of an increasingly urbanised world (Grimm et al., 2008)? Perhaps, as Menno Schilthuizen rightly argues through his book Darwin Comes to Town, urban ecosystems are assembling themselves and might one day be the chief form of nature on our urbanised planet.

References

• Britannica. (1998, July 20). metamorphosis. In Encyclopedia Britannica. Retrieved June 29,2023 from https://www.britannica.com/science/metamorphosis
• Calhoun, A. J. (2014, September 29). Dragonflies and helicopters?. Neuroecology. https://neuroecology.wordpress.com/2014/09/29/dragonflies-and-helicopters/
• Davies, G. R., & Richards, W. O.  (1957). Imms’ general textbook of entomology (10th ed., Vol 2). Chapman and Hall. 
• Exploration Films. (2021, September 26). Incredible Creatures That Defy Evolution 3 | David Hames | Dr. Jobe Martin [Video]. YouTube. https://youtu.be/4y1BAqOnhMM
• Grimm, N. B., Faeth, S. H., Golubiewski, N., Redman, C. L., Wu, J., Bai, X., & Briggs, J. a. G. (2008). Global Change and the Ecology of Cities. Science, 319(5864), 756–760. https://doi.org/10.1126/science.1150195
• Hook, P. (2008). A concise guide to insects. Parragon Books Ltd.
• Kaleka, A. S., Kaur, N., & Bali, G. K. (2019). Larval Development and Molting. In IntechOpen eBooks. https://doi.org/10.5772/intechopen.85530
• Kautt, C. (2011, September 4). Copying the Creator. WordPress. https://cetministries.files.wordpress.com/2011/04/sep-oct-2011-copying-the-creator-helicopters-and-dragonflies.pdf
• Kowarik, I. (2011). Novel urban ecosystems, biodiversity, and conservation. Environmental Pollution, 159(8–9), 1974–1983. https://doi.org/10.1016/j.envpol.2011.02.022
• McGavin, G. C. (2000). Insects. Spiders and other terrestrial arthropods. Dorling Kindersley Inc.
• Nazneen. (2019). Dragonflies and Damselflies. Penguin Random House.
• Oldroyd, H. (1979). The lives of insects. In Insects: An illustrated survey of the most successful animals on earth. (pp. 118-182). Hamlyn. 
• Schilthuizen, M. (2019). Darwin comes to town: How the urban jungle drives evolution. Picador.
• Whalley, P. (1979). The orders of insects. In Insects: An illustrated survey of the most successful animals on earth. (208). Hamlyn. 

Featured Image Credit: CUES

Acknowledgement

Special thanks to Researchers at CUES, especially Fizala Tayebulla and Dr. Ojit Kumar Singh Mayanglambam for their research on the insects of the Dheerpur Wetland Project Site.