Thursday, 4 February 2016

156. Troides aeacus (The Golden Birdwing)

Number: 156
Family: Papilioniidae
Sub-Family: Papilioniinae
Species: Troides aeacus (C. & R. Felder, 1860)
Common name(s): The Golden Birdwing
Photography location: Tam Dao foothills (Vinh Phuc Prov.)

This is the commoner species of Troides, occurring throughout the country in a wide variety of habitats and altitudes, even being present in towns. 
This species can easily be distinguished from Troides helena in the male by the more acute anal angle of the hindwing, and the peppering of black scales at the edge of the golden yellow discal patch near the anal angle, which is not found in helena
The females can be separated by examining the black markings at the base of the hindwing. In aeacus this extends into the hindwing below the cell, whereas in helena it fills space 7 but does not enter space 1 below the cell. The female of aeacus also has a yellow discal spot in space 7 of the hindwing, which is absent in helena.
Below some shots of a female caught in July 2015 at Tam Dao (Tây Thiên). I haven't took photo of male yet.

 Female Troides aeacus

Same individual in hand, close-up on underside HW
Note the yellow discal spot in space 7 (absent in helena) and the black coloration in space 1 below the cell (yellow in helena).

Underside HW of female helena, for comparison.

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