358 



THE STRUGGLE FOR EXISTENCE 



animal. Tliis resemblance is a protection, because the 

 weaker animal is taken l)y its enemies for the animal which 

 it resembles, and C()nse(|uently goes unharmed by them. 

 The succeeding generations of the weaker animal come 

 more and more to imitate the stronger, until, hnally, we 

 oiu'selves have difhculty in (hstinguishing one from the 



other. A l)utterfly, 

 known as the vice- 

 r( )y, imitates another 

 and larger butterfly, 

 known as the mon- 

 arch. The monarch 

 has reddish lirown 

 wings, two inches 

 long, with black 

 veins. It also has a 

 peculiar odor which 

 is very much disliked 

 by birds, hence it is 

 let alone by them. 

 Now, if an(.)ther but- 

 terfly should grow to 

 look like the mon- 

 arch, even though it 

 had no jieculiar odoi', it would be less lialjle to l.)e eaten liy 

 birds, l)ecause the birds, having grown to know the monarch, 

 Would tliink th;d, tliis other butterfly was also a monarch 

 and would let it alone. lOxactly this thing has hapjiened. 

 The viceioy has grown to resemlik^ the monarch so closely 

 that only a very observant ])erson can tell them apart, 

 and pi-o])ably birds do not know one from the other, hence 

 touch neither. iSee Figure 237. 



Fig. 237. — Moiiurrli l)UttcrH\- uI»i\h' and vi 

 rij\' below. Nvic the resemblance. 



