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Wings aflutter

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From emitting smells, to camouflaging and even poisoning predators, butterflies have excellent survival strategies up their sleeves... er, wings.

Butterflies — delightful splashes of colour fluttering about. But there is more to them than just being dainty, flying jewels.

Female butterflies are excellent botanists. They can smell plants using their antennae and taste them with their legs, where certain sensory cells are located. So, a female butterfly will only lay her eggs on the leaves of those plants that serve as food for the caterpillars that will hatch. Caterpillars, though voracious eaters, are fussy and specific about their choice of food plants. Perhaps, this is nature’s way of ruling out competition among the different species.

The first thing caterpillars eat, is their egg shell. What’s more, they also eat their own skins. Now, you may wonder how and why they do so. Their non-stop eating ensures that they grow rapidly, and in no time, their skin gets too tight. So, like snakes, they shed their skin and acquire a new one. But unlike snakes, they eat up their old skin too (like a snack between meals), following nature’s golden rule — nothing is wasted in nature.

Escape artist

Now, here is a typical scene in the life of a caterpillar of the common Mormon butterfly: it is busy chomping on the lemon plant leaves, its preferred food. Along comes a hungry lizard, shooting its long sticky tongue in and out of its mouth. The little fellow freezes in dread. But, the lizard walks right past its potential prey. Why? The caterpillar is disguised as bird poop, all gooey and in dark green and white.

A few days later, the same caterpillar, having grown out of its skin twice, now dons a different avatar — it no more looks like bird poop. Its new skin is shiny green, matching the shade of the lemon leaves. Now, comes along a little bird. It spies the juicy, plump caterpillar. Just as it is about to grab it, the little dare-devil raises its head threateningly, exposing two large false eye spots to frighten the bird. (In reality, its eyes are tinier, hardly visible, as it tucks its head under its body). But the threat does not frighten the bird. The caterpillar now has another trick up its ‘sleeve’: it shoots out a fiery red fork like structure,called osmeterium, from its mouth like a dragon. The osmeterium gives off a foul odour. The startled bird backs away and looks for something else to eat.

Caterpillars of the Lycaenid group of butterflies use a different strategy of self-defence. They use the services of bodyguards: ants. Ants protect and look after these unarmed, defenceless caterpillars, even leading them to the tenderest leaves of the plants. But, nothing comes for free. The Lycaenid caterpillars pay for their protection by giving off a sweet secretion from their rear ends when the ants tap them there with their antennae. This irresistible reward, ‘honey dew’, is greedily lapped up by the ants.

The fifth time the caterpillar is about to moult, it transforms itself into a pupa or chrysalis. Some pupae look exactly like small leaves, well camouflaged, while some look exceptionally pretty, like the shiny golden pendant-like chrysalis of the common crow butterfly. Either way, they are safe from potential predators.

Adult butterflies too use various strategies to keep their enemies at bay. The most amazing of all being the blue oakleaf butterfly. When it rests with its wings folded, it looks exactly like a dry leaf, complete with the veins and fungal spots. No bird would want to eat a dry leaf. But, if the bird comes too close for comfort, the butterfly exposes its upper wings, a flashy blue, and flutters away, leaving the predator too stunned for action.

Some butterflies, like the common rose, accumulate poisons in their body by feeding on poisonous plants when in the caterpillar stage. As adults, they advertise this fact by having bright colours which are ‘warning’ predators, to keep away. If by chance a bird eats a poisonous butterfly, it will suffer a nasty sensation. Once bitten twice shy, and so, it will never attack a brightly coloured prey again. Now, here comes the twist in the tale. There are other butterflies that are not poisonous, but mimic poisonous ones. They appear to have identically coloured wings, with the same patterns as the poisonous butterflies to fool predators.

Truly, the strategies of survival amongst butterflies, like many other creatures, can be mind-boggling.

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Printable version | Dec 9, 2019 6:04:39 PM | https://www.thehindu.com/children/wings-aflutter/article27782714.ece

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