21 July 2019

Yeomen of Singapore

Yeomen of Singapore
Featuring Singapore's Yeoman butterflies

When I wrote the 1st edition of the Butterflies of Singapore and launched it back in 2010, the extant species from the Cirrochroa genus was only one - the Banded Yeoman (Cirrochroa orissa orissa). References from the early authors indicated that there was only one other species listed from Singapore, the Malay Yeoman (Cirrochroa emalea emalea), but this was described as "have not been taken again in Singapore during the present century" referring to the period from 1901 to 1999.

Subsequent to the publication of the book, a sighting of the Malay Yeoman was recorded in the Central Catchment Nature Reserves in Nov 2013. This was followed by many more observations of this species over the years, suggesting that there is now a viable colony of this species and it is no longer a seasonal migrant in Singapore. There were many sightings of this species in 2018 and even as recent as March 2019 from Bukit Timah Nature Reserve.

Another species, the Common Yeoman, was first sighted at the Singapore Botanic Gardens in May 2015 and a breeding colony continued to exist for over 6 months, with several individuals encountered over this period. Its life history was successfully recorded from this colony. A confirmed sighting was made as recent as Apr 2018, and it is believed that this species can also be considered as a resident species rather than a seasonal migrant or a vagrant. The Common Yeoman was a new discovery for Singapore as it was previously not recorded by the early authors.

This blogpost introduces the three extant Yeoman species in Singapore.

1) The Banded Yeoman (Cirrochroa orissa orissa)

The Banded Yeoman was the only representative of the Cirrochroa genus prior to 2013. Even so, it is moderately rare and only found in the forested areas of the Central Catchment Nature Reserves. Sightings of the Banded Yeoman are sporadic, but regular, and the appearance of this species is rather local in distribution.

The Banded Yeoman is skittish and alert to any movement towards it. It has a habit of perching on the underside of leaves and opening and closing its wings. It is observed to puddle at damp footpaths, feeding on forest flowering plants and sunbathing at sunlit spots under the forest understorey.

The upperside of the Banded Yeoman is ochreous brown with a black apical border and a prominent broad yellow post-discal band. The underside is paler with markings reflecting the upperside of the wings. The upperside of the hindwing bears prominent black spots with scalloped black marginal and sub-marginal lines.

2) The Malay Yeoman (Cirrochroa emalea emalea)

Recorded as a seasonal migrant, it is now believed that the Malay Yeoman is a resident species in Singapore, with regular sightings of the species throughout the year. Another forest-dependent species, the Malay Yeoman displays similar characteristic behaviour as its closely related species, the Banded Yeoman. It is often observed to stop on the underside of leaves with its wings folded upright. It is also observed to puddle at damp footpaths.

The Malay Yeoman is fulvous orange on the upperside with black marginal borders on both wings. A distinctive orange sub-apical spot on the forewing above is a key diagnostic feature of this species. On the underside, the silvery post-discal band is constricted in spaces 5 and 6, which separates this species from another lookalike, Cirrochroa malaya malaya.

One of the habits of the Malay Yeoman is to perch under a leaf upside down

A puddling Malay Yeoman

It is curious to have two closely associated species and I wonder why C. malaya doesn't carry the English common name "Malay Yeoman" whilst C. emalea is the Malay Yeoman. This will probably cause some confusion and perhaps it may be necessary to sort out the common names for these two lookalikes.

3) The Common Yeoman (Cirrochroa tyche rotundata)

Newly discovered in Singapore, the Common Yeoman can be observed at the Singapore Botanic Gardens

The 3rd Yeoman is the most recent to be added to the Singapore Checklist in 2015. It was recorded as a new discovery and may have been a stowaway with the import of plants for the Singapore Botanic Gardens? Its two recorded host plants, Hydnocarpus spp. occur in various parts of Singapore, but rather rare.

A Common Yeoman perched under a leaf with its wings folded upright

The Common Yeoman is fulvous orange on the upperside, but lacks the wide black apical border that the Malay Yeoman has. There is a series of scalloped marginal and sub-marginal black lines and post-discal spots on the hindwing. On the underside, the post-discal silvery band is narrow and more or less uniform in width throughout its length.

The Common Yeoman has been observed to puddle on damp footpaths but can sometimes be seen sunbathing with its wings opened flat. It also displays the same habit of perching under a leaf with its wings folded upright, like the other two Cirrochroa species found in Singapore. However, unlike the other two species, the Common Yeoman is so far the only one that is observed in an urban garden.

There are at least 3 more species of the genus found in Malaysia, and should be looked out for in the forested areas of Singapore. Perhaps one or more may make an appearance in Singapore one day in the future.

Text by Khew SK : Photos by Alan Ang, Khew SK, Koh CH, Loh MY, Horace Tan, Irene Tan and Jonathan Soong