Flying insects can often prove to be a nuisance — mosquito bites cause an itchy rash, a wasp&’s sting inflicts acute pain, flies are singularly disgusting, but dragonflies, with their strange droning noise as they descend on to water, are harmless, with an almost fairy-like appearance and movement. Their flight is so unique that engineers have been inspired to design robots that will fly like them.
These insects have four independent, alternately moving wings and they can fly at speeds of 60 mph. They can shoot up in a perpendicular direction of 20 feet. An amazing observation was recorded by a marine biologist Charles Anderson, who lives and works in the Maldives. In a video-film, Dr Anderson carefully tracked plain-coloured dragonflies, the Globe Skimmer (Pantala flavescens), only to discover they make the longest migratory journey of any insect in the world, flying a distance of 11,000 miles, back and forth, across the Indian Ocean.
Dragonflies, with their delicately fluttering wings, intriguing flight movements and possessing individual beauty, are precious creatures that indicate the health of the environment. Zoologist David Attenborough described how these creatures came into being 300 million years ago in his book, Life on Earth, when our planet’;s vegetation was devoid of trees. Short grasses and shrubs covered the earth back then and insects like dragonflies and crickets adapted to the subterranean depths. Therefore, they moulted, shedding their skins as they grew. This form of shedding skin still occurs with the larvae of the dragonfly.
It was only later, when forests and waterbodies developed, that dragonflies and erstwhile ground insects moved to trees or ponds and rivers. In fact, scientists have theorised that oxygen levels during prehistoric times were about 50 per cent more than it is today. That explained why dragonflies were larger in size at the time. They grew smaller over millennia due to predation caused by prehistoric birds, some of which were big. The ancient dragonfly certainly deserves more respect than we give them, with humankind destroying their habitats.
Both dragonflies and another species related to them, damselflies, require clean water to survive. The aquatic habitats where their larvae hatch and develop will reflect on the condition of the water, depending on whether these insects survive. If waterbodies are contaminated by pesticides or sewage, the larvae will perish soon enough. The fact that dragonflies consume mosquitoes proves how beneficial the insects are to human health. From their ancient giant forms to the present day dainty creatures, dragonflies, by their presence, give us hope of a pollutant-free ecology. To sight these insects in large numbers will indicate that water sources are clean and free from impurities.
It may be prudent to check the status of dragonflies in India, to the extent possible. Let us focus on two states: areas in Assam/Meghalaya and a zone in Bengal. A pilot study was conducted to examine the diversity and distribution of dragonflies from selected sites in Asansol and the Durgapur industrial area of Burdwan district, from January 2012 to December 2015. A total of 57 different species was recorded, writes Amar Kumar Nayak. Despite Asansol and Durgapur being an industrial belt, the study revealed an encouraging number of dragonflies, in terms of diversity. The region has wetlands, grasslands and ponds, making it a conducive zone for dragonflies to flourish. In India, a total of about 500 species of dragonflies has been recorded.
In Meghalaya 33 species were recorded. Bidyut Kumar Das and Sarma Uddipta, students of zoology, had conducted a study of dragonflies in Assam&’s wetlands in Barpeta district, recording 23 species. Although studies on dragonflies in India have been documented from the time of Linnaeus, in the 1850s, not much research was done on the diversity of these insects in Assam. Empirical studies require concerted efforts to check the status of dragonflies throughout Assam&’s vast expanses. According to Fraser (1933), “Life in the tropics would soon become unbearable were it not for the vast numbers of dragonflies acting as scavengers of the atmosphere.”
Incredibly, scientists have discovered more than 5,000 species of dragonflies all over the world, with 450 species in North America alone. Dragonflies belong to the insect order Odonata, from the Greek word meaning “the toothed one”. This refers to the serrated teeth that are the insect&’s mandibles. Their movable heads have large hemispherical eyes that enable them to locate prey with remarkable vision. They defend their territories by a pattern of patrolling, at various heights. Their larvae are aquatic while the adults are predominantly terrestrial.
From 300 million years ago to the present incorporates the incredible odyssey of the dragonfly, which once upon a time lived in a world with no forests; and then the gradual shift to a combination of terrestrial existence and an aquatic life, flying around the earth and across its oceans.