590 



Color and Pattern and their Uses 



lines or striae. These striae vary in distance apart, on different scales, from 

 .0007 mm., as in the scales of the great blue Morpho butterflies, to .004 mm., 

 as in the sulphur-yellow butterfly, Catopsila eubule. 



The scales cover (in all but the few ''clear- winged" moths) the wings 



on both upper and lower sides, 

 being insecurely attached to the 

 wing membrane by having their 

 short pedicels inserted in little 

 pockets or cups on the wing sur- 

 face. They show an interesting 

 and varying manner of arrangement. 

 This arrangement varies from an 

 extremely uniform one in the but- 

 terflies and higher moths to one 

 of much less regularity of disposi- 

 tion in the lower moths. On the 

 wings of a butterfly the scales are 

 inserted with their pedicels directed 

 toward the base of the wing in 



trans- 



FIG. 772. A small, partly denuded part of 



the wing of a butterfly, Lycena sp., showing subparallel rows running 

 the scales and pits in a wing membrane, yersely across the wing, i.e., from 

 into which the tiny stems of the scales are . . . , 



inserted. (Photomicrograph by George O. anterior to posterior margin, and 

 Mitchell; greatly magnified.) the scales in each row are at 



approximately equal distances apart. Their distance is less than the width 



of each scale, so that adjoining scales 



overlap laterally and thus make each row 



to be composed of two tiers of scales, an 



upper and an under one: the insertion- 

 cups of one tier are very slightly but per- 

 ceptibly advanced beyond those of the 



other tier. The scales of the upper tier 



alternate with those of the lower tier, and 



each upper scale overlaps laterally two 



under ones. But in addition to this 



lateral overlapping, the distance between 



the rows of insertion-cups is less than 



the length of the scales, so that there 



is an overlapping of the tip of the 



scales of one row over the bases of the 



scales in the next row in front. By this 



double overlapping there is formed a complete shingled covering of scales 



over each surface (upper and under) of each wing. 



FIG. 773. Bits of denuded wing of a 

 butterfly, Grapta sp., to show rows 

 of insertion- pits on upper and lower 

 sides, with three scales in position. 

 (Greatly magnified.) 



