440 



THE ANIMALS AND MAN 



Some butterflies have blue or green or purple colors, 

 iridescent and changeable, on their wings. The common 

 little "blues" have the upper side of the whole wing metallic 

 blue. Examine under the microscope some scales from 

 one of these blue wings, or from a blue or greenish iridescent 

 spot on any butterfly's wing. They will be seen to be not 

 blue or green (as long as light is allowed to come from the 



mirror of the micro- 

 scope up through 

 them) but either color- 

 less or of a pale yel- 

 lowish or brownish 

 shade. But if the 

 light from below is 

 cut off by placing a 

 hand over the micro- 

 scope mirror they will 

 show an iridescent 

 blue or green. 



Examine under the 

 microscope a bit of 

 wing from which most 



Fig. 226. A small, partly denuded part, of the SCaleS have 

 much magnified, of a wing of the small j^^gj^ rubbed (figS. 

 blue butterfly, Lycaena sp., showing the ^ ° 



scales and the pits in the wing-mem- 220 and 227 j. iNOte 

 brane, in which the tiny stems of the scales rOWS of tiny pitS Or 

 are inserted. (Photo-micrograph by G. O. pockets in which the 

 Mitchell.) ^ 



Stems of the scales 

 fit. The scales are fastened, though not very firmly, 

 to the wing membrane by their stems, and are ar- 

 ranged in fairly even rows. In each row they are so thick 

 that they overlap each others' sides, and the rows are so 

 close together that the tips of the scales of one row overlap 

 the bases of those of the one in front. This arrangement 

 is much like that of shingles on a roof, and each wing is 



