Tale of Two Swallowtails

March 15, 2014

We were on a walk along the muddy path to the bridge at River Tern Lodge, Bhadra, with Vijay, who works as a naturalist there. Bhadra Tiger Reserve is a beautiful, dense, green forest which immediately fills you with a sense of wonder. The campus at River Tern Lodge itself is home to many a story and in some cases like this, a complete life-story.

01-earlierForm

Earlier form

It was a rather humid day. We weren’t even walking fast but were dripping with sweat as though we‘d had a tough workout. Along the path, we stopped to see a colourful caterpillar, which would ultimately turn into the Common Mime butterfly. We usually learn about the four stages of a butterfly’s lifecycle. But in the larval stage itself, the caterpillar undergoes different transformations, each form being known as an instar. This caterpillar we came across wasn’t at its final instar.

When a butterfly lays eggs, she chooses plants on which the caterpillars can feed. Such host plants are different for different species of butterflies.

Common Mime butterfly

Needless to say, the caterpillars do complete justice to the feeding. They eat the leaves, munching their way to grow bigger and bigger, and shed their skin. The shedding of the skin is called moulting and the skin left behind is a ‘moult’. This colourful, bright caterpillar we saw had probably moulted twice or thrice before. Its current form had it coloured 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 more fat and bright caterpillars. These Common Mime caterpillars were very different from the one we’d seen earlier. We found the black-orange-white moult next to one of them. They are also known to eat their own moults.

Pre-pupatory larva with shed skin

Butterflies face several threats from predators, parasites and parasitoids. They use three main techniques to protect themselves:

Camouflage (click here for some brilliant examples of 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 also vomit. The bird won’t forget this and surely will 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.

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.

Alseodaphne semecarpifolia

A few days passed after which the munching 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’.

Bent larva before transformation

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.

There, in front of our eyes, was a bright caterpillar; twisting, wriggling, squirming and transforming to look like 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.

Pupa with silk girdle

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 though it is growing out of the branch or twig. A perfect camouflage – one of nature’s many wonders.

Burnt and broken twig

Vijay, who works as a naturalist at River Tern Lodge, is a keen student of nature and an enthusiastic learner. Vijay kept a watchful eye over Common Mime caterpillars. He noticed an interesting point that the breeding season for Common Mime ranges from May to end of September. Five months is a long breeding cycle for this butterfly.

Camouflaged pupa

We were able to see two moults of the caterpillar and also its transformation to a ‘twig’, and all of this within the campus. The sheer genius of the camouflage speaks for itself.

The ‘twig’

Vijay never stops looking, and his eyes caught something else. There is a lemon tree next to the staircase leading to the reception. He saw a bright green caterpillar on the leaves, identifying them to be that of the beautiful Blue Mormon. If it feels threatened, this caterpillar juts out a deep-red, forked, fleshy and possibly foul-smelling organ called the osmeterium.

Blue Mormon larva

While we stood admiring Vijay’s find, he showed us something else – there was more than one instar of the Blue Mormon; some on the leaves, some under the leaves, and some hidden in dark, green corners.

Blue Mormon instar and Image

Blue Mormon instar

Slowly a group gathered around the lemon tree, everyone whispering, every now and then someone softly calling out, “Hey, I found a caterpillar”. The olive-green body of the caterpillar is shiny and has uric-acid-like whitish markings which help the caterpillar mimic fresh bird droppings.

Blue Mormon mimicking bird droppings

Vijay signalled to the enthusiastic group to see where he was pointing – It was a pupa, getting set to transform into the lovely Blue Mormon.

Blue Mormon pupa

Lokesh, who mans the boat and has been developing vision like the birds he is so familiar with, was all smiles. He had found a leaf that still had some eggs on it, though it was later identified as those of another butterfly.

We saw eggs, caterpillars in their various instars, pupa, and later, the adults themselves – all in a span of 48 hours.