Metamorphosis at my doorstep

Somebody had planted it there -- the Scarlet Milkweed. Didn’t give much thought to it. Noticed only when it bloomed with bright yellow-orange flowers, garnished with vividly coloured caterpillars. These were the larvae of the Plain Tiger (Danaus chrysippus), a species of Danainae ("milkweed butterflies", which lay their eggs on various milkweeds, on which their larvae feed) and a subfamily of the brush-footed butterfly family, Nymphalidae.

Scarlet milkweed (Asclepias curassavica) also known as Bloodflower and Indian Root is native to South America but has spread across many parts of the globe. Its flowers attract many butterflies. The plant’s sap contains toxins, which in turn are transferred to the caterpillars, making them inedible to most predators. The caterpillar of the Plain Tiger sports bright colours that warn predators of its bad taste.

The adult Plain Tiger lays eggs on the undersides of leaves. The eggs hatch after approximately five days and then the larval stage begins with the first instar of the caterpillar. Instars are the stages between moults. The skin of caterpillars, like those of insects, don’t grow as the animal grows. In order to grow in size, the caterpillar moults (sheds old skin exposing the new layer of skin underneath) four times, moving from the first instar to the second, the second to the third, and so on until the fifth and final instar. During these moulting stages the caterpillar grows incredibly in size, as its only function is to be an eating machine.

During the fifth and final instar, the caterpillar will look for a suitable spot to pupate (pupa is the third stage in a butterfly’s lifecycle). Once it locates the ideal spot, it hangs inverted, forms the shape of a ‘J’ and moults for the last time. The new skin underneath will form the chrysalis, which is the pupa of a butterfly formed of a hard chitinous shell (chitin is a tough, protective, semitransparent naturally occurring polymer, which forms the principal component of arthropod exoskeletons). The pupa may be green or brown if found in natural surroundings; otherwise it is pink. Although it looks dormant, a lot happens within the pupa. This is the stage where the caterpillar metamorphoses into an adult butterfly.

A caterpillar in its final instar getting ready to moult one last time

The chrysalis

After approximately two weeks in the chrysalis stage, the butterfly emerges. Known in this stage as the imago, the sexually mature adult frees itself from the chrysalis and settles nearby to wait for the wings to gain full shape and size. The butterfly's wings are small and wet when it emerges. Fluids are pumped from its abdomen into the wings so that they expand to their actual size. While this is happening, a brownish liquid may be seen coming out of the butterfly; this is meconium (a waste product from the pupal stage that is expelled through the anal opening of the adult butterfly). The wings then have to dry and become warm before the butterfly can exercise its flight muscles. All of this takes only a couple of hours.

The meconum can be seen flowing down

The imago against the empty chrysalis

Now that the Plain Tiger is in the last stage of life, its sole purpose is to seek a mate and breed. Although the Plain Tiger had put on its best suit, the same could not be said of the Milkweed. All that was left of the plant after the caterpillars had eaten their fill were bare stems stripped of leaves.

But milkweeds are hardy plants, and there is no cause for worry. They will bounce back to their former glory in no time.

Text and photographs by Arun Menon

Balcony Bugwatch - The moron, the lightbulb and the Potter Wasp

You must be familiar with that old joke: How many morons does it take to change a lightbulb? The answer shall be illumined presently to the patient reader of this post. 

But first, the story of a sting operation. 

Apart from a long line of little black ants bearing whitish larvae to the safety of another crevice in the wall, there are other insects at work in my balcony. One is a species of Potter Wasp. Sometime in December, my daughter (to her utter alarm) observed an adult wasp fashioning a nest with damp earth. It buzzed in and out of the balcony tirelessly bearing bits of wet mud in its jaws. Over several days this building material was adeptly patted down into a hollow structure with many tubular chambers. One of these cells remained open at one end even after the nest was finished. The structure was cemented to the base surface with mud, which I suspect had been mixed with the insect's saliva and possibly something else that acts as a resilient binding agent. 

The moist part that you see in your picture (above) dried up in a few hours and turned to quite the same colour and texture as the rest of the nest. The adult soon disappeared and has not been seen for over two months now. I assumed she had fulfilled her corporeal assignment and ended up in the food chain of the bee-eaters often heard trilling about nearby.

Enter the moron with the mission of changing a lightbulb. Since the wasp had fastened its nest to the clamp of the lampshade in the balcony, I couldn't change the lightbulb even if I wanted to. Having seen no action for over two months, I decided to inspect the shade. I couldn't do that without disturbing the nest. Presuming it to be empty, I chipped away at it with an old kitchen knife, hoping to detach it cleanly and add it to my collection of souvenirs taken (without menace, may I add) from the natural world. 

Chipping away the nest proved more challenging than I had expected. At one butter-fingered juncture, the blade of the knife bent at the tip. At the next barbarous hack, the nest gave way and fell to the floor, smashing into two or three uneven fragments with catacomb-like  innards.

From one of the cells, a very agitated-looking adult wasp emerged with a rustle of eager wings, shaking off slivers of pupal sheath. Inside the tube from which it emerged were the wispy carcasses of spiders, flies, beetles and other food that the parent wasp had stashed long before its offspring had hatched. After loitering about the balcony muttering revenge, the wasp flew away into the bleak and hostile afternoon.

Assuming the rest of the nest to be empty, I decided to pry some more with my bent knife.

There were two cells remaining in the nest. The one to the left in the picture contained a dead wasp, which had pupated. But I could find only bits of its legs and a hollowed-out thorax. Since the cells didn't seem to have any vestibular passages between them, which ruled out cannibalism by one of the same brood, what had eaten the rest of it? And, since the remains were quite desiccated, how long ago?

The cell to the right vibrated with angry, impatient whirring. As I trained my camera on it, an adult wasp slipped out, deposited small grains of white faeces, and began to explore the territory around it. Then, with a sudden flourish of its new wings, it took off abruptly into the great wide open. My hacking of the nest had yielded two ready-to-fly adults and one dead-on-arrival pupa. Had I not opened the nest, how long would it have taken before they would come out on their own? 

Other questions remain: Did the parent wasp know how many eggs it was going to lay? Or did she build the cells one by one as she laid her eggs, taking breaks to hunt and provide for her brood? Was she able to provide for all the cells? Did one of the larvae die of inadequate nutrition? What about the empty cells? Would the new adults survive? Would the bee-eaters get them?

At the end of the afternoon, only one question was answered: It takes only one moron to change a lightbulb.

Text and photos by Beej