A few years ago, I was observing a Common Mormon (Papilio polytes) butterfly pupa on a curry leaf tree (Murraya koenigii), or kari bevu as it is called in Kannada, next to my house. I was hoping to photograph the butterfly emerging from the pupa. The curry leaf tree is one of the host plants for Common Mormons, and this particular tree was infested with caterpillars.
On that fateful day, I noticed something tiny moving atop the pupa. On closer inspection, it turned out to be a wasp. I wasn’t sure what the wasps were doing, but I decided to set up my camera anyway, just in case.
I noticed that the wasps were moving around a tiny hole in the pupa. Then I realised that a Pteromalid wasp had previously parasitised the pupa and laid eggs within it. The wasp larvae had fed on the common Mormon pupa and had metamorphosed into adults within the pupa. These adults were emerging from the pupa now.
Several species of wasps parasitise Common Mormons. Ichneumon wasps lay eggs within the caterpillar, and their larvae feed on the live caterpillar until they pupate. Chalcid wasps infect the pupal stage, while mason wasps anaesthetise the caterpillars and carry them to their nest to use as a living food larder for their larvae.
As time went by, I noticed that the wasps were periodically looking inside the hole. As more wasps started emerging, it became clear to me – the newly emerged wasps were larger and bluish in colour, whereas the wasps which I had seen previously were golden-green in colour. I had only seen the male wasps before, the females were emerging just now.
The males went into a frenzy, with two or three males attempting to mate with the same female. I was having trouble focusing on the wasps. The males were only two or three millimetres in length, and the females were four to five millimetres. Even with a macro lens, they appeared tiny in the image.
After mating, the females flew off in search of new victims.
Before I knew it, the entire event was over. Around 2 hours had elapsed from the time I had observed the first wasps till the time the last wasp left.
A few minutes after the wasps left, a couple of ants discovered the pupa. They enlarged the hole already made by the wasps and started feeding.
Finally, the ants left too, leaving behind a desecrated pupa. What should have matured as a vibrant butterfly was now an empty husk.
A few days later, I noticed a butterfly flying from one leaf to another. It was a female Common Mormon laying a fresh clutch of eggs.
The eggs are almost always laid on the underside of freshly sprouted leaves. The yellowish-green egg matches the colour of the leaves, and as it is underneath the leaf, it can’t be easily seen by predators. The newly emerged caterpillars feed almost exclusively on fresh sprouts, moving downwards and consuming more mature leaves only as they grow older.
This time the caterpillar did not fall prey to any predators or parasites, and successfully metamorphosed into a butterfly.
The cycle continues!