ORDER LEPIDOPTERA. 



143 



veins, one of which has three branches running parallel with 

 the edge. As the weight or pressure of the air while mak^ 

 ing the stroke is borne chiefly by the front of the wing, it 

 needs these rods to strengthen it. 



The scales of a butterfly's wing differ much in shape on 

 different parts of the body. On the wing of the Cecropia 

 moth the hairs of the body and base of the wing are seen 

 to pass into broad scales, represented in Fig. 172, They 



FIG. 173. Arrangement of the scales on a moth's wing, a, some enlarged. 



are attached to the wing and laid partially over one 

 another like the tiles on a roof, being inserted in irregular 

 rows.* 



The caterpillar or larva of the Turnus butterfly may be 

 found on the apple or birch and other trees. In July the 

 butterfly lays a nearly round egg (Fig. 107, .4) upon the 

 leaf, and by the end of summer one may find the great 

 green worm in the same place. The body is round, fat, 

 and smooth; there are twelve segments behind the head. 

 From the top of the segment next to the head is projected, 



* According to Dr. Koyston-Piggott, the foot-stalk or pedicel of a 

 scale consists of two membranes united to form a tube which gathers 

 up and distributes the nourishing fluid among the striations or ribs of 

 the scale. The scale has been resolved into a series of latticed ribs, 

 connected by irregular cross bars; each rib displaying double black 

 margins, and the cross bars often beaded. The scales of Lepidoptera 

 make admirable tests for the highest powers of the microscope. 



In the scales of MorpJio cypris " the cross-bar structure, like all these 

 azure blues, is most delicate, and produces glorious color." Papilio 

 troilus " is worth close investigation for reticulated bars." (Micro- 

 scopical Advances, xxvii.; English Mechanic, Nov. 11, 1887.) 



