Now You See Me, Now You Do not
A No-Model (or Small) Grass Yellow (Eurema brigitta senna) feeding on the flower of the Coat Buttons (Tridax procumbens)
A Pitcher Blue (Virachola kessuma deliochus) perched on the fruit of the Singapore Rhododendron (Melastoma malabathricum)
On this weekend’s blogpost, we check out three extant species which might be comparatively small in dimension, and unlikely to be migratory or stray species within the native setting. Nonetheless, after showing for a brief time frame, two of those species haven’t been noticed for a few years thereafter. Having been recorded by the early authors, these species weren’t reliably recorded for a lot of a long time, till the interval between 2006 and 2009, when two of those species had been noticed in very localised areas in Singapore.
A White Fourline Blue (Nacaduba angusta kerriana) perched on a leaf within the forest understorey
Then they disappeared, and weren’t seen for a few years since. It’s not recognized the place they disappeared to within the meantime. As they don’t seem to be all forest-dependent species, the place do they go to? Maybe in some localised space the place they haven’t been noticed but? Or have they got some kind of hibernation mechanism of their life-history biology that enables them to delay eclosion for a very long time?
A feminine No-Model Grass Yellow ovipositing on its host plant. Cassia mimosoides
Curiously, once they appeared in Singapore, all their life histories had been recorded on their respective caterpillar host crops. Their life histories are documented right here on this weblog. From the information which might be proven right here, their early phases are fairly regular and there may be nothing out of the strange that means that they’ve particular traits in comparison with different butterflies.
1. The No-Model (or Small) Grass Yellow (Eurema brigitta senna)
A feminine No-Model Grass Yellow feeding on the flower of the Coat Buttons
The No-Model Grass Yellow (additionally known as Small Grass Yellow) was a recorded as a re-discovery in 2006 when it was noticed at an open patch of land in Punggol that was cleared for future improvement. Its caterpillar host plant, Cassia mimosoides grew wild as a “weed” within the space. For a interval of about as much as a 12 months or so, the species was fairly frequent at that website, and mingled with lots of the city and scrubland butterfly species.
A feminine No-Model Grass Yellow ovipositing on its host plant, Cassia mimosoides
Right this moment, a brand new public residential challenge is underneath building on the website, and the open wasteland with secondary forest progress is now not there. With that, the No-Model Grass Yellow has disappeared. Efforts had been made to domesticate its host plant in varied locations, and the caterpillars and pupae translocated to the opposite websites, however to no avail. The species has not been seen for a very long time since then.
Upperside of the No-Model Grass Yellow displaying the scalloped black borders
A male No-Model Grass Yellow perched on a leaf. Word the heavily-speckled wings
The species appears to be like similar to lots of its different Eurema cousins which might be frequent throughout Singapore. The primary completely different on the upperside is that the black borders are often scalloped, not like the deeply excavated black borders of the opposite species. On the underside, there aren’t any cell spots, and the wings are closely peppered with brown freckles throughout. The underside of the feminine is extra distinctive in that the hindwing is a paler yellow than the forewing.
2. The White Fourline Blue (Nacaduba angusta kerriana)
A White Fourline Blue perched on a leaf
The following characteristic species is a small butterfly with a wingspan of solely about 30-35mm. The White Fourline Blue was once more, recorded as a re-discovery in 2009 at Telok Blangah Hill Park. It was a shock because the species was documented as an extant species in Singapore by the early authors, however was not seen till 2009 – and even so, at an city park. Was it one of many remnant species that survived regardless of the city improvement in Singapore?
When it appeared, there have been a number of people fluttering across the shaded shrubbery, and we even encountered a mating pair of the species, suggesting that there was a small, however critically-endangered colony in that location. Happily, our life histories professional, Horace Tan, noticed a feminine ovipositing on its host plant, Entada spiralis and managed to doc its life historical past efficiently.
Upperside of a newly-eclosed feminine White Fourline Blue
The male White Fourline Blue is purplish blue above with a skinny black border. The feminine has a broad black border on the forewing, and a lightweight blue to whitish floor color with diffuse greyish markings on each wings. The feminine is so distinctive that it can’t be confused with another species within the Nacaduba genus. The underside is greyish floor color with broad white diffuse markings. There’s a distinguished black rounded submarginal spot in house 6 of the hindwing.
3. The Pitcher Blue (Virachola kessuma deliochus)
A Pitcher Blue perched on the flower of the Coat Buttons
In contrast to the previous two species, the Pitcher Blue is an extant uncommon species that was re-discovered within the early 1990’s at a website close to the character reserves in Chestnut Forest. It was subsequently noticed at Kent Ridge Park and different areas within the Southern Ridges. It was solely till it was once more noticed at Bukit Batok Forest that its life historical past was recorded.
The species relies upon solely on the caterpillar host crops from the Nepenthes genus – generally known as Pitcher Crops or Monkey Cups. These crops favor hilltops and reasonably dry, rocky areas to develop. Right this moment, these crops are usually not frequent (as a consequence of habitat destruction and poaching) and this has probably affected the survival of the Pitcher Blue. That the caterpillars feed contained in the seed pods of the Pitcher Plant makes it even tougher to outlive with out the plant, and the truth that the plant has to flower and fruit as effectively!
Upperside of a feminine Pitcher Blue
The male is a deep shining blue above with a broad black apical border on the forewing. The feminine is a lightweight greyish-blue with narrower borders. The underside is gray with the everyday white striae, resembling the Nacaduba species. The hindwing has a filamentous white-tipped tail at vein 2 of the hindwing. The Pitcher Blue continues to be occasional sighted, significantly at flowering bushes just like the Syzygium however sightings are erratic and it is probably not seen for a number of years earlier than one other one turns up once more.
The place are these species of butterflies at the moment? Are they nonetheless lurking round someplace, undiscovered, in some patch of greenery in our parks and nature reserves? Why have they disappeared for years on finish? When will they reappear once more? Solutions to those questions proceed to elude us as we attempt on to battle to additional our information and understanding of our butterflies to assist preserve them for future generations.
Textual content by Khew SK : Pictures by Khew SK and Horace Tan
Life Histories :