Color and Pattern and their Uses 591 



This close placing and overlapping, and the small size of the scales, 

 bring it about that the number of scales on a single wing is truly prodigious. 



FIG. 774. Diagram to show shingled arrangement of scales over surface of butterfly's 

 wing; the short black bars indicate scales in cross-section; the broad central bar, 

 the wing in cross-section. 



In Morpho sp., for example, the distance apart of the lines of insertion-pits 

 on a bit of the upper wing surface taken from the middle of the fore wing 

 is .151 mm.; the distance apart of the pits in a line is .043 mm. (on the 

 under surface the pits are .05 mm. apart); so that in a space 25 mm. by 

 25 mm. (i square inch circa) there would be 165 lines of scales with 600 scales 

 in each line, or 99,000 scales to each square inch of wing-surface. As the 

 upper and under surfaces of the fore and hind wings combined equal about 

 15 square inches, the total number of scales on the wings of Morpho may 

 be roughly approximated at 1,500,000. 



The pedicels of the scales are of slightly varying shapes and of different 

 lengths, corresponding with the pockets into which they fit. Those which 

 enter insertion-cups which are expanded at the base, or at some point between 

 the base and the mouth, present at the tip or be- 

 tween the tip and the point of merging into the 

 blade of the scale, respectively, a slight expan- 

 sion, so that they are pretty firmly held in the cup 

 by a sort of ball-and-socket attachment. The 

 scales are held in position by the elasticity of 

 the cups which closely clasp the pedicels. After 

 death of the moth or butterfly this elasticity is 

 largely lost, by desiccation of the wing mem- ^j 

 brane, and the pedicels are more easily brushed Morpho sp. (Greatly mag- 

 from the wing than when the insect is alive. 



Now to pay attention to the actual structure or make-up of individual 

 scales. When studied carefully under the microscope singly and in cross- 

 sections of the wing the scales are seen to be tiny flattened sacs, composed 

 of two membrances, enclosing sometimes only air, sometimes pigment 

 granules attached to the inner face of one of the membranes, and some- 

 times (as observed in cabinet specimens) the dry remains of what may have 

 been during life an internal pulp. The striae are confined to the outer mem- 

 brane (that farthest from the wing-membrane) and are probably folds in 

 this outer membrane. These striae are plainly elevated above the inter- 



