20 August 2010

Butterfly of the Month - August 2010

Butterfly of the Month - August 2010
The Blue Nawab (Polyura schreiber tisamenus)



The month of August is an important month for Singapore as its National Day falls on the 9th of August annually. This year is Singapore's 45th birthday, and it was a particularly happy occasion as Singapore came out strongly from the global recession with a double digit GDP growth for the quarter and the year looks bullish for a strong economic performance.



Other than a few days of the exceptionally rainy weather spilling over from July, the month was beginning to show some signs of the waning "Sumatras" as the intermonsoon winds begin to shift. The inaugural Youth Olympic Games - the first in the games' history, is being held in Singapore from 14 - 26 August as some 5,000 athletes aged between 14 and 18 years, will take part in 26 sporting events.



Our feature butterfly this month, is the majestic and awesome Charaxinae, the Blue Nawab (Polyura schreiber tisamenus). This proud and magnificent butterfly can be described as moderately rare, although it has been spotted with regularity in Singapore - more so than in neighbouring Malaysia.



The Blue Nawab is the less often encountered of the two Polyura species found in Singapore. It is a strong flyer like the Plain Nawab and prefers to remain at high levels. The Blue Nawab has been found in urban parks and gardens, forested areas and also within mangrove areas. The males of the species have been observed feeding on decomposing animal matter but are also attracted to overripe fruits.


The Blue Nawab has a silvery underside marked with brown and purple patterns. The upperside has a white median band ornamented with blue. It possesses two pairs of tails on the hindwings. The female of the species is usually larger often attaining a wingspan of 80mm, with broader and longer tails.



The species has a robust body, and like a typical Nymphalidae, has only four fully-developed legs for walking. The forelegs appear more brush-like and are not used for walking.


The butterfly is usually very skittish, and can fly powerfully for long periods of time. Unless one encounters a recently-eclosed individual or in a feeding mood, photographing the Blue Nawab is often a challenge.


Unlike the Plain Nawab, the Blue Nawab does not display territorial behaviour where it perches on a few favourite spots and returns to those spots time and again after chasing away intruders. Where observed, the Blue Nawabs are almost always in full flight, as if in a hurry to go somewhere.


The caterpillar of the Blue Nawab has been found and bred successfully on a variety of plants. Amongst these are Acacia auriculiformis, Adenanthera pavonina, Chorisia speciosa, Nephelium lappaceum, Bauhinia kockiana and another unidentified plant. Hence it is quite interesting that the caterpillars can feed on so many common plants, and yet the species is not as common as it should be.


Text by Khew SK : Photos by Khew SK, Simon Sng, Horace Tan and Tan Ben Jin

8 comments:

Atsu said...

I am so happy to read this latest update about the magnificent butterfly. I sometimes spotted its caterpillar though, the number of the caterpillar always comes with one, barely more than two. I can't even find more from the other neighboring host plant trees too. So when you mentioned that interesting fact of this butterfly is the butterfly is not as common as its ubiquitous host plants. I am curious what factors play the pivotal role to decide the number of this butterfly.
I know there is assamensis. What is the difference between Polyura schreiber tisamenus and assamensis?
Yours, Atsu

William B. Folsom Photography, Inc. said...

It is always amazing that the color combinations of butterflies are so beautiful, so diverse, and so different. The capture of these images helps create an interest and awareness of this beauty that surrounds us all no matter where we live. Thank you for the photos and the descriptions.

Commander said...

Thanks, Atsu. Glad that you've managed to spot the caterpillars! Perhaps the species is very vulnerable to predation by parasitic wasps/flies that reduce their population significantly.

Some of the regional subspecies are "questionable" as they look exactly the same. A lot depends on the source and the original authors' explanation of why they consider it a subspecies. You will have to look for the paper that describes the subspecies assamensis and form your own conclusions.

Thanks William for your kind words and support.

X_on_the_map said...

Sigh...So lovely.

Atsu said...

Happy New Year 2011 and may this new year be more fruitful for all the butterflies in Singapore and all of us!

I had a sad event this morning from two Blue Nawab pupae I was raising from stage three caterpillars for a month. One morning, two became in pupation at the same time. I was a bit mystified by the timing because each caterpillar's growing stage was not the same. One is bigger and advanced in terms of growth stage. Then, there was a strange color change in both of the pupae pretty soon. To my sadness, I spotted many(8 from two pupae) maggots mercilessly crawling on the bottom beneath them this morning.

I just wonder if they already caught the parasites when I found them(they were still very small) or were put eggs of parasitic flies on their body later. I kept two caterpillars without net protection in my indoor kitchen feeding Red Saga's leaves.

Your advice will be the most appreciative and thankful.

Thank you.

Atsushi

Commander said...

Hi Atsu,

A pity to hear that your two caterpillars were parasited. It happens very often in the field, and it's perhaps one of the reasons why this species is not as common as it should be, since the caterpillars feed on several host plants.

I have personally seen and documented a parasitic fly laying her eggs into the egg of a butterfly that was just freshly laid! So, besides these parasitic flies and wasps laying their eggs into caterpillars, I believe that all the early stages of the butterflies are vulnerable.

We normally breed caterpillars in plastic boxes or aquariums to ensure that the chances of them being parasited is kept to a minimum.

Cheers and good luck with your next breeding opportunity!

Atsu said...

Thank you for your kind advice on my question about the parasite on caterpillars. I should be impressed by the ingenious way of survival skills for these parasite wasps and flies though, I still feel sad about the way those caterpillars couldn't fully materialize their beautiful potentiality...

I am simply amazed how frequently the Blue Nawab's caterpillars are already falling prey to the parasitic flies. These caterpillars look so laid back. They don't show much interest in hiding themselves from others and prefer staying on the upper side of the leaves.

I was a bit curious about the fact that more common, the Plain Nawab needs far shorter time to be an adult butterfly than the much rarer Blue Nawab.

Again, thank you for your thoughtful advice and cheers!

Yours,
Atsushi

yokki said...

Hi, AtsushiSan
We are trying to reach you. How are you doing? We are going to Singapore this week from Friday.
We hope we can see you again.
Y. Nakamura