Dragonflies
Dragonfly is a clever engineering design of nature which is better designed for flying rivalling even a modern helicopter.
Dragonflies are powerful and agile fliers, capable of migrating across oceans, moving in any direction, and changing direction suddenly.
In flight, the adult dragonfly can propel itself in six directions: upward, downward, forward, back, to left and to right.
They have four different styles of flight.
A number of flying modes are used that include counter-stroking, with fore wings beating 180° out of phase with the hind wings, is used for hovering and slow flight. This style is efficient and generates a large amount of lift. Phased-stroking, with the hind wings beating 90° ahead of the fore wings, is used for fast flight. This style creates more thrust, but less lift than counter-stroking; synchronized-stroking, with fore wings and hind wings beating together, is used when changing direction rapidly, as it maximizes thrust; and gliding, with the wings held out, is used in three situations: free gliding, for a few seconds in between bursts of powered flight; gliding in the updraft at the crest of a hill, effectively hovering by falling at the same speed as the updraft; and in certain dragonflies such as darters, when "in cop" with a male, the female sometimes simply glides while the male pulls the pair along by beating his wings.
The head is large with very short antennae.
It is dominated by the two compound eyes, which cover most of its surface. The compound eyes are made up of ommatidia, the numbers being greater in the larger species. The number (ommatidia) can be as high as 25,000 of varying sizes.
It has an amazing sight and we perfected catching them by tail as kids. We could do that because there were so many 60 years ago.
In other words all its activities are on the wing, eating, drinking, mating, just fooling around and dogfights.
It
is amazing that one of the oldest insects of our world developed all
these skills which the man cannot reproduce by machine. Of course the
300 million odd years of existence made them much versatile.
Its
armory in catching prey is much better than military design. The lower
jaw has a huge, extensible labium, armed with hooks and spines, which is
used for catching prey. This labium is folded under the body at rest
and struck out at great speed by hydraulic pressure generated by the
abdominal muscles.
I thought of writing this simply because this was the first insect that ventured into my water garden on the rooftop for laying eggs.
In the beginning there were only blue one, then a brown one started coming and perhaps a third one yellow in colour. All the other insects including butterflies started coming much later and the birds were the last.
No bees at all.
I did not know they clean up our mosquitoes and larvae.
There is a significant reduction in the mosquito population and I thought my guppies were doing an onerous job.
Not really, dragon fly nymphs can clean up my fish too.
Dragonfly nymphs vary in form with species and are loosely classed into claspers, sprawlers, hiders, and burrowers.
Their internal hydraulic system is better than water sprayer or a pump.
Whereas damselfly nymphs have three feathery external gills, dragonfly nymphs have internal gills, located around the fourth and fifth abdominal segments. Water is pumped in and out of the abdomen through an opening at the tip. The naiads of some clubtails (Gomphidae) that burrow into the sediment, have a snorkel like tube at the end of the abdomen enabling them to draw in clean water while they are buried in mud. Naiads can forcefully expel a jet of water to propel themselves with great rapidity.
1. Dragonflies were some of the first winged insects to evolve, some 300 million years ago.
2. There are more than 5,000 known species of dragonflies, all of which (along with damselflies) belong to the order Odonata, which means “toothed one” in Greek and refers to the dragonfly’s serrated teeth.
3. In their larval stage, which can last up to two years, dragonflies are aquatic and eat just about anything—tadpoles, mosquitoes, fish, other insect larvae and even each other.
4. At the end of its larval stage, the dragonfly crawls out of the water, then its exoskeleton cracks open and releases the insect’s abdomen. Its four wings come out next.
5. Dragonflies are expert fliers. They can fly straight up and down, hover like a helicopter and even mate mid-air. If they can’t fly, they’ll starve because they only eat prey they catch while flying.
6. The flight of the dragonfly is so special that it has inspired engineers who dream of making robots that fly like dragonflies.
7. Most of the adult dragonflies live for only a few weeks.
8. Nearly all of the dragonfly’s head is eye, so they have incredible vision that encompasses almost every angle except right behind them.
9. Dragonflies, which eat insects as adults, are a great control on the mosquito population. A single dragonfly can eat 30 to hundreds of mosquitoes per day.
10. A dragonfly called the globe skinner has the longest migration of any insect—11,000 miles back and forth across the Indian Ocean.
11. Fossils of very large dragonfly ancestors in the Protodonata are found from 325 million years ago (Mya) in Upper Carboniferous rocks; these had wingspans up to about 750 mm (30 in). About 3000 species of Anisoptera are in the world today. Most are tropical, with fewer species in temperate regions.
