Blue Triangle Butterfly | ©Steve Axford (Australia)
A couple of the spectacular Graphium sarpedon, commonly known as the Common Bluebottle or Blue Triangle. The one flying (with the white strands) is the male.
These swallowtail butterflies (Papilionidae) are found in South and Southeast Asia, as well as part of Australia .
The Blue Triangle Butterflies have wings which are black to dark brown in color with large blue area in the middle. Those blue patterns joint to make a triangle and this comes their common name .
A study on the subspecies Graphium sarpedon nipponum indicates that their wings contain the bile pigment sarpedobilin, which causes the blue/green colored wing patches. Locally the bile pigment is combined with the strongly blue-absorbing carotenoid lutein, resulting in green wing patches and thus improving camouflage. In the dorsal forewings, the colored patches lack the usual wing scales, but instead have bristles. On the ventral side most of these patches have very transparent scales that enhance, by reflection, the wing coloration when illuminated from the dorsal side. These glass scales furthermore create a strongly polarized iridescence when illuminated by obliquely incident light from the ventral side, presumably for infraspecific signaling .