TlUi GBASSUOPPER 



19 



resemble dry leaves, blotches looking like mildew are found. 

 Even the legs may 1 )e thin and 

 expanded so as to rescmljle 

 foliage. In our countrj' occur 

 only the twiglike, wingless 

 forms known as walking-sticks 

 (Fig. 13). These walking- 

 sticks change color to corre- 

 spond with the changes of 

 twigs from season to season ; 

 for the young walking-sticks, 

 which appear in the spring, are 

 green like young twigs, but in 

 the autumn the adults are gray 

 or brown. This likeness of 

 animals to things outside of 

 the animal kingdom has been 

 called protective resemblance 

 and has probably Ijecome 

 established because of the 

 freedom from attack which it 

 gives to its possessors. Our 

 common northern species feeds 

 on leaves, especially those of 

 the oak. Occasionally it does 

 much damage to trees. 



The long-horned grass- 

 hoppers and katydids (Locus- 

 tidffi) are closely akin to the 

 type studied. The family in- ,, 



Fig. 1.3. — The northern walking 

 eludes many grasshoppers stick" (Diapheromera Jemorata). 



