The Angled Castor (Ariadne ariadne ariadne)
A female Angled Castor showing its unique underside wing patterns
We are well into the second half of 2026 as the days and weeks fly past so quickly. July 2026 will go down in history as the month of the 2026 FIFA World Cup. Held once every 4 years, the 2026 World Cup is the first time the event was expanded to 48 teams instead of the 32 team format. The tournament was jointly hosted by the United States, Canada and Mexico, the first men’s World Cup staged across three countries. The entire event lasted over 39 days with 104 matches played. Spain won the 2026 FIFA World Cup, beating defending champions Argentina 1–0 after extra time in the final on 19 July 2026.
As the late-night soccer TV binges fade away and the celebrations of the winners end, life goes back to normalcy for the soccer fans. The tenuous peace plan in the Strait of Hormuz is unstable, with neither the US nor Iran willing to stop hostilities in their now 5-month war. Whilst news about the frequent attacks no longer dominates world news, most of the world continues to feel the pinch of rising costs caused by oil price increases and disruptions due to the war.
The US launched a new series of tariffs on trade across the globe, again affecting many countries and causing uncertainty in the world economy. Even tiny Singapore was hit with a new tariff of 12.5% and this time, the tariffs were imposed in the name of forced labour supply chains of manufactured goods. Whilst it was reported that roughly one-third of Singapore's domestic exports are affected by this new tariff, it adds more uncertainty to the companies that export goods to the US.
Back in Singapore, the news that dominated headlines was when Acting Minister-in-charge of Muslim Affairs Muhammad Faishal Ibrahim resigned on 20 July as a minister, MP and PAP member after an investigation into interactions with a woman. Whilst the authorities assessed that neither party had committed a criminal offence, Prime Minister Lawrence Wong said Mr Faishal’s conduct had fallen below the standards expected of a political office-holder. However, the online exchanges between the two still remain confidential, and sparked off speculations and false news on social media, and has people wondering what was it that Mr Faishal wrote that was "inappropriate".
Anyway, back to our seemingly more peaceful butterfly world again. July seems to be a good season for butterflies in Singapore, with a bumper crop of photos of a good variety of species being posted on the local social media platforms. Our feature butterfly for July 2026 is the Angled Castor (Ariadne ariadne ariadne) It was first re-discovered in Oct 2013 at a small forest patch in the Mandai/Ulu Sembawang PCN vicinity. Listed on the early authors' checklists as extant in Singapore, the Angled Castor was not seen until then.
Subsequently, a colony of the species was discovered on Pulau Ubin just a short walk from Butterfly Hill. The Angled Castor, as its name suggests, is dependent on the Castor Oil Plant (Ricinus communis). This plant was found growing in abundance near a storage site on Pulau Ubin. Several individuals were regularly seen at this area, and caterpillars were also spotted on the host plants.
Healthy growth of the Castor Oil Plant on Pulau Ubin. Unfortunately, the land is now cleared for development.
The seeds of the Caster Oil Plant, from which the toxin, Ricin can be extracted
Commercial castor oil is pressed from the seeds of the Castor Oil Plant and then processed. It is rich in ricinoleic acid, an unusual fatty acid that gives the oil its characteristic thickness and chemical properties. The seeds naturally contain ricin, an extremely toxic protein. Ricin attracts attention because very small quantities can be dangerous if they enter the body. In practice, its notoriety comes mainly from assassinations, intimidation and attempted mail attacks.
On the upperside, the Angled Castor's wings are orangey to reddish brown and traversed by five or six narrow and sinuate black lines. A single black discal line lies just beyond the cell-end on both wings. Superficially, it resembles the more common Chocolate Pansy (Junonia hedonia ida) in flight and sometimes be overlooked due to its resemblance. Both species are skittish and challenging to photograph.
The Angled Castor was first re-discovered at Mandai forest area in 2013.
On the underside, the wings are pale crimson brown and crossed with several irregular bands in darker coloration. Small whitish wing scales are featured dotting the wing surface, in much greater abundance in the female than the male. A prominent white sub-apical spot is featured in the forewing on both under- and uppersides.
The patch of Castor Oil Plant on Pulau Ubin has now been cleared, with a small row cultivated at the foot of Butterfly Hill. Although the Castor Oil Plant is not often a popular plant to be cultivated in parks and gardens, the absence of this host plant may spell the doom for the Angled Castor in Singapore. It is hoped that NParks will continue to cultivate a limited quantity of these plants on Pulau Ubin to sustain a population of this butterfly in Singapore.
Text by Khew SK : Photos by Khew SK, Koh CH, Loh MY, Simon Sng, Michael Soh, Horace Tan and Tea YK
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