In the last few weeks, there has been an influx of caterpillars of the butterfly Papilio polytes Romulus, commonly known as Common Mormon, on a Curry Leaf (Bergera koenigii) plant in the balcony area. The first one was spotted on 17 April at its pre-pupatory larva stage. Despite daily monitoring, the emergence of the butterfly from the pupa was missed, and an empty pupal case was found 10 days later. Another caterpillar at a late instar stage was observed on the plant but was missing the next day. This Wednesday, 3 additional early instar caterpillars were found on the plant.

(a) 4th instar caterpillar	(b) 5th instar caterpillar	(c) Pre-pupatory larva	(d) Empty pupal case
Fig. 1 (a-d): Various stages of the caterpillars and pupae seen in the past few weeks

To date, this remains the sole species of butterfly in Singapore that utilises the Curry Leaf plant as its host. This Curry Leaf plant was originally abandoned by someone in the basement of my apartment block. When I brought it home over five years ago, it was infested with whiteflies. To effectively eliminate the whiteflies, I removed all the leaves, leaving only the stem intact. A few months after the leaves regrew, the whiteflies reappeared, prompting me to repeat the leaf removal process. Fortunately, the plant demonstrated remarkable resilience. It subsequently underwent a period of psyllid infestation in October 2020, during which I had to trim the plant again.

In June 2023, the plant began to flower for the first time. I subsequently collected several ripe fruits to obtain seeds, which I then planted in a smaller pot. As of today, I have another pot containing a few Curry Leaf plants. Remarkably, one of the offspring in this pot has begun to flower (Fig. 2) this week at a height of just 40 centimetres, despite being housed in a small pot. Currently, the parent plant stands at approximately 120 centimetres tall. Additionally, there is a caterpillar present on the smaller potted specimen.

(a) 27 April 2025	(b) 3 May 2025	(c) 7 May 20225	(d) 7 May 20225
Fig. 2 (a-d): Flower buds and flowers of the Curry Leaf plant (Bergera koenigii)

In the recent past, the botanical name of the Curry Leaf plant was Murraya koenigii. The change to its current name, Bergera koenigii likely occurred around 2021 [1]. A plant that closely resembles the Curry Leaf plant is Clausena excavata (Pink Wampee) tree. Both plants belong to the same family, Rutaceae. Young Pink Wampee trees can easily be mistaken for the Curry Leaf plant. Additionally, the Pink Wampee tree also serves as the host plant for the Common Mormon butterfly. I documented my observations on this butterfly and the Pink Wampee tree in February 2015.

I had considered removing the smaller pot of the Curry Leaf plant to make space for other plants, as I already possess a larger specimen. However, since the smaller plant has begun to flower, I have decided to retain it until it completes its fruiting cycle, at which point I will determine whether to continue keeping it.

Reference:

[1] Esser HJ. Taxonomic notes on the Rutaceae of Thailand. Thai Forest Bulletin (Botany) 2021;49:27-31. | Read article |