Expert Insight
Issue 6, September 2002 by Simon Chan
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Common Name
Scientific Name
Family
Subfamily
Discovered by
Polymorphism |
: Blue Nawab
: Polyura schreiber tisamenus
: Nymphalidae
: Charaxinae
: Godart in 1824 (the species ‘schreiber’) and Fruhstorfer in
1914 (the subspecies ‘tisamenus’)
: No |
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he rarer of two known species from
the genus Polyura in Singapore, this insect is a medium sized butterfly
with black wings above which is easily identified from the other,
especially in set collections as the white median band is ornamented
with blue. On a predominantly grey under surface, the side that you
usually see of this species while at rest, this white band is replaced
by a silvery one. A dark brown band borders this silver one near the
wing bases.
All species from this genus is characterised by having stout bodies with
strong wing muscles that give them their trademark energetic and swift
flight. While the second species, i.e.
Polyura hebe plautus always
return to the same vicinity where it was spotted, this species never
seemed to stay long at any one area. Both however, can be clearly
differentiated from each other even when in flight because hebe has an
overall brown coloration with a lime green band while schreiber looks
black with a white band.
Of considerable interest is its life-history, in terms of the lifestyle
as well as the physical appearance of its caterpillar. Its green larva
weaves a silken pad on a few of the hostplant leaves to create some sort
of a home base from which it will rest during the day and where it
returns to after a night of feasting elsewhere. With two pairs of
reddish brown spiny horns on its head and a broad orange yellow band on
the 3rd abdominal segment, its appearance is reminiscent of an alien
creature from outer space. Its pupa is less striking, looking more like
a green berry.
Records indicated that it was first bred in Singapore on Rambutan (Nephelium
lappaceum) by D’Abrera in 1958. It was later confirmed by Lee in 1960
and again by Igarashi. Past authors were puzzled as to why its
caterpillars were not found on legumes like the rest of the Polyura
species but BIG’s discovery on 1st January 2002 (please see Sightings)
confirmed that it does. On that day, we found three caterpillars
mingling with numerous hebe ones on a small Saga tree (Adenanthera
pavonina). And to prove once and for all that Saga is really an
alternative hostplant, we took them home to rear. Unfortunately, one was
parasited. However, the other two survived the whole process including
emergence of the adults from their pupae.
Although this handsome creature ranges from India, down south to
Peninsula Malaysia and the Philippines, it is more frequently
encountered in Singapore than the mainland. |
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