362 



Handbook of Nature-Study 



Willow cone-galls. 

 Photo by Verne Morton. 



enlarges into an oblong room. The caterpillar feeds upon the substance 



of the stem until it attains its growth, and then seems to dimly realize 



something about its future needs. At 



least it cuts, with its sharp jaws, a little 



oval door at the upper end of its house 



and makes an even bevel by widening 



the opening toward the outside. It 



then makes a little plug of debris 



which completely fills the door; but 



because of the bevel, no intrusive 



beetle or ant can push it in. Thus 



the caterpillar changes to a helpless 



pupa in entire safety ; and when the 



little moth issues from the pupa skin, Spherical gall of goldenrod, 



,, -, , -. 1 -i 1 i opened, showing its pros- 



all it has to do is to push its head pwous looking owner. 



against the door, and out it falls, and Photo by M . v. siingeriand. 



