Wednesday, December 12, 2012

Life Cycle of Common Rose (Pachliopta aristolochiae)

This individual has been quite intriguing since day one, simply because a Crimson Rose (Atrophaneura hector) was seen hovering around the plant Aristolochia indica, when the egg was collected at Jalahalli. Two of us, Nitin R and myself, watched the Crimson Rose lay eggs on the plant and took two individuals to raise. But as this turned out to be a Common Rose, we assumed that it must have been laid by a Common Rose previously on the same plant, before the Crimson Rose got there. The individual taken by Nitin, on the other hand, turned out to be a Crimson Rose.

The caterpillar hatched five days after the egg was taken from the plant.
Day 1: Size measurement: 1mm

Day 6, the caterpillar moulted for the first time. Instar 2. Size measurement: 5mm

After this moult, the caterpillar gained a more velvety texture of skin, and the colours looked more vibrant.
Moulted once again on day 9. It is observed that the ratio between the size of the face cap to the size of the rest of the body increased with each moult.

On day 11, the caterpillar showed preference to the leaf stalk instead of eating the lamina. This behaviour lasted the whole day. The size was 12mm. The colours grew more and more vibrant each day.

Moulted once again on day 12. Instar 3. Measured 12mm. Post this moult, the eating speed of the caterpillar increased exponentially. The caterpillar did nothing but eat, eat, and eat.

The increasingly vibrant colours could attribute to the fact that it needs to warn the predator of its distasteful contents. Bright colours in nature generally indicate that the creature is not the one to prey upon due to its toxic body contents. On day 17, the length measurement was 25mm.

Cannibalism is a known phenomenon amongst caterpillars. There was another caterpillar of Common Rose in the same container as this individual. This caterpillar had formed silken thread (pre-pupa stage) and had fixed itself to the wall of the container in order to pupate. As this stage immobilizes the caterpillar, it is easy for the other to feed on. So, the caterpillar on observation here, partially ate up the other caterpillar which had formed pre-pupa. This is the dead caterpillar.

On day 28, the caterpillar formed silken thread on a twig kept inside the box, and hung itself upside down. Before this, the length of the caterpillar measured 32mm.

It stayed that way till the end of day 29. The colours had dulled down and it gained the pre-moult appearance.

It is strange that this individual did not form a cremaster (a firm attachment to the surface of the twig/container, built with strong webs). It pupated without the cremaster, and was hanging down from the twig.

On day 29, at 3:27pm, the caterpillar started pupating. The process was done by 4:00pm. It was bright red in colour when freshly formed.

Just after pupation. The black structure on top of it is the last moult.

The next day, on day 30, the pupa was dry and had changed appearance to a brownish shade, which would be the most amazing camouflage in any natural conditions. It was perfectly woody. A lateral view of the pupa.

A ventral view of the pupa on day 30.

On day 45, the pupa turned partially transparent and the forewings could be seen through the pupa. This transparency is an indication of nearing eclosion.

On day 46, the pupa eclosed and the adult Common Rose emerged. (Eclosion process was missed!)

The discarded pupa after eclosion:

Total time taken for the life cycle: 50 days
Egg: 5 days
Caterpillar: 29 days
Pupa: 16 days

It was an absolute pleasure to watch the beautiful adult Common Rose fly high up in the sky.