Flying aces of the insect world
They are the master of all aerial manoeuvres; they are the master hunters. They are dragonflies and damselflies
Foring! The name elicits excitement, joy and adventure. The vibrant flutterer did always throw up challenges in the chasing and catching pursuit of a kid. They come in iridescent colours, large bulbous eyes, long, slender tails and strong veined wing pairs.
The insects that we lovingly call foring in Bangla are of a specialist and ancient flying order – the Odonata. In layman's terms, they are recognised as dragonflies and damselflies.
The first flyers
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Dragonflies are the first among the insect kingdom to have conquered the aerial domain. Evolved in the Carboniferous era around 250 million years ago, the dragonfly wings exemplify the triumph of insects over both land and air.
They set the invertebrate state of art for flying. The mastery of flying does not involve simply roaming around; with aerial expertise, these insects vie for the best hunter award.
Dragons in the air, dragons underwater
Both dragonflies and damselflies have dual modes of life. They lay eggs in water and live there until adulthood.
For other creepy-crawlies, this is bad news. For scientists, it is a remarkably complex and equally interesting life cycle. Life in dragonflies exhibits three stages: Egg, nymph and adult.
The first two are always aquatic, gill-breathers and a much-prolonged form than its adulthood stage.
The free-flying terrestrial lung breathers are what we see around and it constitutes only one brief stage of its life. Having said so, all three equally predate any prey fit under their mandible.
Assassin-class adaptations
Dragonfly nymphs go for several moults before merging into a flier. Unlike the scooper and chaser adults, soft-bodied juveniles are ambush killers and for this, they have the ability to walk along the waterbed. Surprisingly, as grown-ups, dragonflies give up walking.
They can sit, but cannot walk, their legs being angled at 45° to catch prey in mid-air. Compound eyes become large and domical to ensure a broad range 360° view. All four of their wings are extraordinarily uncoupled.
The wings have no connection with each other and can beat up independently. Dragonflies can hover and turn 180° while in flight and fly backwards. The helicopter we see today is a giant mechanical dragonfly on its own.
Who is who?
Based on body structure, Odonates are divided into two major suborders, viz: Zygoptera (damselflies) and Anisoptera (dragonflies).
To keep the chronicle simple, damselflies are delicate and comparatively weaker with narrow, equally proportionate weaker wings than other counterparts.
The dragonflies are more robust and much larger in dimension. Both subgroups have many families, some of which can stand as the most graceful insects.
The enigmatic yet least known
Of about 5,900 worldwide known dragonfly and damselfly species, merely 600 have been well documented in the Indian Subcontinent. In Bangladesh, odontology, the study of dragonflies and damselflies, is still sprouting.
Being a country from subtropics, the marshes, swamps, ditches, ponds, lakes and estuaries of Bangladesh offer an ideal residence for these insects and a rich place to study odontology.
A strong string in the web
In addition to its aesthetics, dragonflies and damselflies are indispensable parts of the food web.
The aquatic nymphs are the chief predators of dipteran maggots—the juvenile gnats, midges, mosquitoes and flies. The adult flies are always treated as a delicacy for the grown-ups. Therefore, the next time you see dragonflies, they are doing pest control for free!
Conversely, the nymph and adult warrior flies are naturally preyed upon by numerous shorebirds, herons, storks, bee-eaters, kingfishers etc respectively.
Without them, the larger animals would be in dire straits. Dragonflies are valuable bio-indicators and efficient pest repellents. Their life is interlaced with water. Many of them are strictly habitat-specific, their presence or absence can reveal what is going on in the web of life.
The dragonflies and damselflies are now winning science's spotlight. Dragonfly enthusiasts in Bangladesh are increasing day by day. You can also join in!
When, where and how
Where to observe
Odonates belong to diverse habitats. Water bodies such as ponds, ditches, tanks, streams and rivers, the undergrowths along those banks and fully set-up gardens with good sunlight are the perfect places to see the dragons and damsels.
When to observe
Best time to watch Odonates is during midday, especially when the sun flares up after a drizzle. Being sensitive to thermoregulation, they stay most active during this time. Most of the species of this region may be observed from May to November.
How to observe
Odonate species are harmless – devoid of any kind of sting, magnified mandible or noxious liquid-emitting appendages. Due to their extremely sensitive eyes, it is better to wear dull coloured outfits while going on a nature walk.
Highlight
Adult Odonates are the only hexapods that cannot move on foot. Adults have their legs bent at 45° angles with a longitudinal body axis. Odonates are the sole exception among insects that can propel each of their four wings independently. This gives them the capability of extreme manoeuvrability, including sharp twists and turns and even the ability to fly backwards.
