Autumn Leaf is a recent discovery here in Singapore. The original
subspecies, Doleschallia bisaltide pratipa, was recorded by the
early authors, but was not seen in Singapore since the beginning of the
20th century and believed to have gone extinct. The recent discovery
of the Autumn Leaf has some difference from the Malaysian subspecies. The characteristic subapical
white spots are usually not present (at least not all the 5 spots) in the
subspecies pratipa and siamensis, both found in Malaysia.
This discovery is therefore not likely to have come down from the north. This
subspecies was discovered within the nature reserves and appear to be colonising
more areas and is becoming more frequently encountered. Eggs and
caterpillars have been found on the Common Asystasia (Asystasia gangetica)
and bred to adulthood. One possible hypothesis is that the species could
have escaped from the Butterfly Park and managed to breed on the very commonly
found host plant which is found all over the island as a wild weed.
However this theory is only speculative and without hard evidence.
Nevertheless, Singapore is now endowed with another resident species, which
is hopefully here to stay!