178 THE FUNDAMENTAL ASPECT OF COLORATION 



2. The Morpho type, in which the lamellae are situated in the 

 vanes (or ribs) and are inclined towards the base of the scale 

 (Fig. 64). This type of structure has been demonstrated very 

 convincingly by Suffert. A brilliant highly metallic blue is the 

 prevailing colour, and, according to the last-mentioned observer, 

 it is connected with the peculiar reflecting properties of the 

 individual ribs, since it shows its full intensity and lustre on an 

 isolated rib or on ribs which have become laterally twisted, and 



Fig. 65. Scale of Entimus type (schematic). A, multiple thin films, 

 the seat of the colour. B, cuticle enclosing lamellar structure. 

 (After Mason.) 



consequentl}^ does not depend on their arrangement or proximity 

 to other ribs on the scale. Onslow, who paid a large amount of 

 attention to scales of this type, concludes that in the arrangement 

 of the ribs they show a regular periodic structure of the correct 

 theoretical magnitude ; the thickness of the ribs and of the air- 

 films between them varies from one to three half wavelengths. In 

 other words, he claimed that the ribs and the air layers between 

 them behaved as multiple films placed on edge. He did not 

 apparently recognise the lamellar structure of the individual vanes 

 or that a single rib is capable of giving the full colour. Mason, who 



