Golden Birdwing Shot at Seam Reap, Cambodia

[David Chan]

Dear Dr Seow,

Are these male and female Troides aeacus thomsoni or Troides aeacus thomsonii or Troides aeacus aeacus? How do you tell them apart? These photos were shot at Siem Reap, Cambodia. Thanks.

25075

25076

Best regards,
David Chan

[Psyche]

These are Troides aeacus aeacus which range from India to most of mainland SE Asia.
http://www.ifoundbutterflies.org/media_images/TroidesAeacus/01TroidesAeacus_KrushnameghKunte_an907.jpg
http://www.ifoundbutterflies.org/media_images/1a_7/a-29068.jpg
http://yutaka.it-n.jp/pap/10040001.html
The veinstripes are wider & prominent in both sexes of this ssp. & the HW spots narrower.

The 2nd SE Asian ssp malaiianus is found in peninsular Malaysia(Malaya) & part of southernmost Thailand.
The veinstripes on the FW are rather obscure on the upperside especially in the male . The HW spots of the female are rounder.
The male is rather rare & somewhat small, often closer to the size of the Common Rose.
http://nlliew66butterflies.blogspot.my/2014/01/the-golden-birdwing-troides-aeacus.html
http://yutaka.it-n.jp/pap/10040010.html
http://swallowtails.net/

The name thomsonii or thomsoni is considered invalid.

Bates first described this subspecies in error as from between Thailand & Cambodia, as variety thomsonii of Troides rhadamanthus from the Philippines.
T. rhadamanthus.
http://insecta.pro/images/1024/25485.jpg

The location error is immaterial but for the name thomsonii to be valid, a 2nd author need to describe & upgrade the name.
It seem everyone thought someone have done it but no one did.

Fruhstorfer described ssp malaiianus from Perak in Peninsular Malaysia.
Taxon malaiianus is taken to be the correct subspecific name.


TL Seow: Cheers.
PS. I did some checking . It is probable Bates ' type specimen came from the Bangkok region & the name thomsonii is invalid because aeacus is an earlier name & have priority.
Why Malayan forms are referred to 'thomsonii' in the past for so long is another mystery.
It may be that Bates' type specimen is atypical & more like the Malayan subspecies.
The difference between ssp aeacus in Thailand & ssp malaiianus in Malaya may not be marked & each can vary a fair bit.

[David Chan]

Dear Dr Seow,
Thanks a lot for the details.

Best regards,
David Chan