I've tried photographing iridescent butterfly wing scales a few times with poor results. I came across a specimen that had several iridescent spots on the wing so I decided to give it another try. The first few efforts were pretty sad looking. So I decided to try a lighting method that has worked well for me with iridescent beetles. I cut a ping-pong ball in half and then cut a hole at the top of the hemisphere large enough for the microscope objective to fit through. I placed the hemisphere over the iridescent section and illuminated it with two fiber optic light guides. Worked out pretty good.
On this specimen, the iridescent scales have a very different shape from the other scales on the wing. They have a curved shape, and the tips are smooth an rounded. The "normal" scales are flat, and have three lobes at the tip.
Again... I am constantly amazed every time I examine this subject.
Top image: 7X objective, 2.5X photo-eyepiece, Canon 10D
Lower image: 10X objective, 2.5X photo-eyepiece, Canon 10D

