206 ELEMENTARY ZOOLOGY 



tions of structure and life-history there is much similarity 

 in the many insects of this order. The eggs are usually 

 laid on the food-plant of the larva ; the larva feeds on the 



FIG. 69. A small, partly denuded part, much magnified, of a wing of a 

 " blue" butterfly, Lyceena sp., showing the wing,scales and the pits in 

 the wing-membrane, in which the tiny stems of the scales are inserted. 

 (Photo-micrograph by Geo. O. Mitchell.) 



leaves of this plant, grows, molts several times, and 

 pupates either in the ground or in a silken cocoon or 

 simply attached to a branch or leaf. There are about 

 six thousand species of moths and butterflies known 

 in North America, and they are our most beautiful in- 

 sects. 



Coleoptera : the beetles. TECHNICAL NOTE. Obtain 

 specimens of various beetles, among them some water-beetles and 

 June-beetles with their young stages, if possible ; if not, then the 

 young stages and adults of any beetle common in the neighborhood 

 of the school. Of the swimming and diving water-beetles there are 

 three families, viz., the Gyrinida? or whirligig beetles, with four eyes 

 (each compound eye divided in two), the Hydrophilidas, or water- 

 scavengers with two eyes and antennas with the terminal segments 



