2o8 THE NATURE-STUDY REVIEW [2 :6-sept., 1906 



small size of the scales, bring it about that the number of scales on a 

 single wing is truly prodigious. In a species of Morpho (one of the 

 great blue Brazilian butterflies), 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 of 25 mm. by 25 mm., about one square 

 inch 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 

 between the tip and the point of merging into the blade of the scale, 

 respectively, a slight expansion, 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 pedi- 

 cels. After death of the moth or butterfly this elasticity is largely 

 lost, by desiccation of the wing membrane, 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 individ- 

 ual 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 membranes, enclosing sometimes only air, 

 sometimes pigment granules attached to the inner face of one of the 

 membranes, and sometimes (as observed in cabinet specimens ) the 

 dry remains of what may have been during life an internal pulp. The 

 stria; are confined to the outer membrane (that farthest from the 

 wing-membrane) and are probably folds in this outer membrane. 

 These striae are plainly elevated above the interstrial space. All scales, 

 excepting some scent-scales on male butterflies, possess these longitu- 

 dinal striae, which traverse the scale from base to outer margin and 

 are very sharp, and separated from one another by equal distances. 

 The stria; sometimes curve in at the lower angles of the blade, con- 

 verging toward the origin of the pedicel; in other cases they fade out 

 at these angles. In scales of the common Monarch butterfly Anosia 

 plexippus from 33 to 40 stria-, averaging .002 mm. apart, are present 



