SCALE OF THE WING OF THE AZURE BLUE BUTTERFLY

SLIDE: BY C.M. TOPPING c. 1860

FROM: Collection of William Rutt, c. 1860

The scale of the Azure Blue Butterfly was listed in Hogg of 1854, as sold by C.M. Topping, and noted to be from Polyomatus argus. According to Hogg, these scales are from the underside of the wing and are a a very good test of the defining power of a 1/4 inch object glass. Using substage oblique illumination, my 20X S-plan objective seems to fit this definition and its image is shown next to the engraving from Hogg's book, revealing about the same detail. Like Morpho menalaus, the blue color is a consequence of diffraction and interference resulting from the three dimension strucure of the scales. It is therefore only evident only with top lighting. The use of the term Azure Blue can be quite confusing today, as it also is used to describe the South and Central American butterfly, Morpho menalaus.