Color and Pattern and their Uses 
59 1 
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. (1 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¬ 
brane, and the pedicels are more easily brushed 
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- 
w 
Fig. 775.—Base of scales: a, 
of Gloveria arizonesis; b, of 
Morpho sp. (Greatly mag¬ 
nified.) 
