batesian mimicry | aranyaparva

The twig

June 25, 2013 at 4:24 am (Butterflies, Camouflage)
Tags: Alseodaphne semecarpifolia, batesian mimicry, Bhadra, burnt and broken twig, butterflies, camouflage, Common Mime, india, jungle lodges, metamorphosis, Papilio clytia, pupa, river tern lodge, twig

“Hey, look what we had missed!” exclaimed our friend. We were on a walk along the muddy path to the bridge which connected the 2 beautiful islands at River Tern Lodge, Bhadra. A walk on a path may sound normal to some, romantic to a few others, routine to the rest. But nature has many a surprise in store and a walk is always interesting and fun. We saw a pair of grasshoppers mating; and they were jumping to different locations while “on the job” 😉 A few meters ahead we found seeds of a tree that had the same fragrance as soap nut; and we passed by a mistletoe tree (you read it right, we passed by it. Rana and I didn’t stand under it then, we had audience ;))

Please click on the images for a larger size

It was a rather humid day. We were dripping with sweat, and we were not even walking fast. Along the path, we stopped to see this colorful caterpillar, which would ultimately turn into the Common Mime butterfly. But this one wasn’t there yet. It had some more eating, growing and shedding to do. When the mother lays eggs, she chooses plants on which the caterpillars can feed (host plant). Different species of butterflies have different host plants. The caterpillars do complete justice to the feeding! They eat the leaves, munching their way to grow bigger and bigger. In fact, grow is an understatement. They outgrow and shed their skin. The shedding of the skin is called moulting and the skin left behind is a ‘moult’. This colorful bright one had probably moulted twice or thrice before and was now in this form, all in black and orange, with white patches.

We reached the bridge and were about to head back. Seeing the voracious feeder had made us hungry. It was then that we saw what everyone had almost missed – two fat and bright caterpillars. A quick check confirmed that they were indeed what we believed them to be – caterpillars of the Common Mime butterfly, very different from the other one, which was a much ‘younger’ caterpillar. We found the black-orange-white moult next to one of them. They eat the moults, by the way. If this change was dramatic enough, the transformation to a Common Mime pupa is phenomenal.

Before we get there, let me share a few tidbits about butterflies.They face several threats from predators, parasites and parasitoids. Three main techniques that they use to protect themselves are:

Camouflage (click here for some brilliant examples of insect camouflage)
Unpalatability – some of the butterflies feed on certain ‘toxic’ plants and hence, become distasteful for their predators. If a predator, say a bird, tries to eat an unpalatable butterfly, it experiences strong heart beats and may vomit. The bird won’t forget this and surely, it’ll avoid such a “bitterfly” 😉
Mimicry

The Common Mime butterfly is a ‘harmless’, palatable butterfly, using mimicry for protection. It resembles either the Common Crow or the Blue Tiger, both unpalatable butterflies, and in turn, ‘visually cheats’ its predators. However, its pupa uses camouflage for protection. We were all set to witness this transformation. The excitement was too much to handle, but we had to wait.

The Common Mime usually chooses saplings with fresh leaves and lays its eggs on the surface. These caterpillars were on the leaves of Alseodaphne semecarpifolia (known as Mashe / Nelthare / Karuvadi in Kannada). The caterpillars munched on the light green, fresh leaves and got plumper by the day.

A few days passed after which the munching seemed to have stopped. They had moved on from the surface of the leaves to rest. One was on a stem and the other was on a twig. These pre-pupatory caterpillars slowly changed their posture and appeared ‘bent’.

Many hours passed. It was 5:30 in the morning; all of a sudden the transformation was there for us to see. We missed the very first bit, but the rest was no less fantastic. Click here for a short video of the transformation from caterpillar to pupa stage.

Closeup of 'twig on twig'

There, in front of our eyes, was a bright caterpillar, twisting, wriggling, squirming and transforming to a ‘burnt and broken twig’! The pupa stood suspended from the twig with a silk girdle. It was like seeing a graceful trapeze artist hanging.

Camouflage is a widely used survival technique by many adult butterflies. This is one of the cases where a pupa uses camouflage. It looks like a dead twig with the top broken off irregularly. It is black, brown and blotched all over. To add to the ‘effect’, the bottom segment appears as it is growing out of the branch or twig! A perfect camouflage, one of nature’s many wonders.

Closeup of the 'twig' on a stem

The 'twig' on a stem The twig

We got to see two moults of the caterpillar and also its transformation to a ‘twig’. It has been one of the most fulfilling experiences in our lives. The sheer genius of the camouflage speaks for itself.