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Journalism of Courage
They have the best eyes in the business, two great big precious stones wrapped around their heads like astronaut helmets, in addition to three small ones called ocelli (highly movement-sensitive) on their foreheads, enabling them to see 360 degrees, so they’ll see you even if you sneakily approach from the rear. Each whopping compound eye has between 28,000 and 30,000 facets called ommatidia, each has thousands of photoreceptors that collect light and send it to the nervous system for further processing. While we have three main light-sensitive proteins (called opsins) one each for blue, green and red which help us see colour, dragonflies have no less than 11, and one extremist species as many as 30. This enables them to see UV and polarised light. Cells sensitive to ultra-violet light may be used to stabilise dragonflies in flight. Some photoreceptors are tuned to low light conditions, especially for species that hunt at dusk. These, like very wide aperture lenses, gather maximum light in poor light conditions but may not have terribly good colour resolution — I suppose like the white noise you get when taking digital images in low light. Also, different opsins may operate or not at various stages of a dragonfly’s life; some dragonfly larvae may hatch in sand and may lack blue opsins because blue light does not penetrate underground.
Compared to us, it’s thought they see in slow motion, some 200 frames per second (the general consensus for human beings is that we see between 30 and 60 frames per second) so they have plenty of time to home in on their target or escape becoming one. Their eyes are divided into two halves: the top (dorsal) section and the lower ventral section, each with its own special arrangement of opsins. Those facing upwards are more tuned to blue and green wavelengths (the longer ones) assisting them in hunting by making the sky appear lighter and making their prey stand out clearly for easier targeting. Each facet points in a slightly different direction as compared to its neighbour, resulting in a composite of slightly overlapping images, though exactly what the dragonfly makes of all these overlapping images, or how it combines them is still not known. All this visionary power comes at a cost and 80 per cent of a dragonfly’s brain is devoted to vision.
This was why I was astounded when I came across two dragonflies that had made an unsuccessful water landing in the pool in Goa. They looked exactly like crashed biplanes, with their fuselages broken, gossamer wings outspread. Had they been flying drunk and simply collided in midair? They are mating like crazy at this time, and I have seen them dip low over the water occasionally kissing the surface: perhaps they were misled by the bright blue reflection of the sky in the water, and the light blue tiles at the bottom, and simply came down too low to attack their own reflections.
I know they lay their eggs on plant stems in water, but there were no plants in the pool. Some species may, perhaps, simply deposit their eggs on the water surface and hence, dip down to do so and go too deep like a jet experiencing a serious, irrecoverable tail strike. Or, which seems more likely had there been a dogfight over the water — they are extremely territorial — and the crashed ones had simply been ‘shot down’ by having a wing disabled? Actually, both combatants would have tumbled down had they tangled in mid-air (like the way raptors like eagles sometimes do), attempting to bite each other’s wings or heads off, and this seems to have been most likely. Once in the water, they are helpless as their delicate wings get waterlogged.
What was a little alarming, however, was when I picked them up, their long bodies seemed to have been softening and dissolving — a tenderising reaction, perhaps to the toxic chlorine being sprinkled in the pool every evening? (No wonder all the other insects and frogs that had fallen in at one time or another, were dead.) And dragonfly abdomens are tough, segmented and designed to absorb the impact of the flying insect hitting prey at speeds of up to 90 kph!
There is certainly much aerial combat in progress over the pool as they guard their personal air corridors — flying up and down on patrol, swiftly chasing away interlopers. I really wonder if they will ever realise that a chlorinated swimming pool is not the ideal habitat to deposit eggs: there are no aquatic plants here and the water is toxic. But it does provide a profitable hunting ground as there are other small insects — and other dragonflies flying over it — upon which to prey. And dragonflies are said to have a success rate of 95 per cent in their hunts.
This story has a slightly sad ending though. Just as I had finished writing my notes about what I had observed and was getting up, there at my feet on the tiles lay a dead dragonfly with its wings outspread. There were no signs of injury. I picked it up and placed it on the balcony railing to photograph it. Before I could, a gentle whisper of breeze whisked it away depositing it on the parapet beneath. Here it lay and then, was taken apart segment by segment by large black ants, till there were only the outspread wings and bulbous head left, like a sort of fossilised image of what once had been. And overnight the wings and head too vanished. Nature’s clean-up crew had done their job.
