12 MAN AND ANIMALS 
crime at all, in so far as the destruction is absolutely unavoidable. The 
wanton and useless destruction of animals not condemned as noxious by 
years of investigation, though probably not forbidden by the example 
of the animal world, is forbidden by the best sensibilities of every civilized 
man and woman. When the value of an animal to us is in question, the 
animal should have the benefit of the doubt, and we should hesitate 
long before introducing animals of supposed value. Certainly, also, 
every animal condemned by careful investigators should be destroyed 
whenever opportunity is presented. Mistaken and sentimental ideas 
cause the killing of many useful animals and the protection of many 
noxious ones. The farmer kills snakes and skunks whenever he has the 
opportunity, though they are among the most useful animals. Shrews 
are master destroyers of mice. Still many people mistake shrews for 
meadow mice and destroy them. Likewise the housewife kills the 
house centipede, the enemy of household pests, as a dangerous and 
repulsive creature even in the absence of any knowledge of the question- 
able charge that it bites young infants. Mistakes are not confined wholly 
to uninitiated individuals. Misjudgment by the officials of the Brook- 
lyn Institute of Arts and Sciences, possibly influenced by the sentiment 
of Longfellow’s mistaken poem on the “ Birds of Killingworth” brought 
about one of the first official introductions of the English sparrow. Thus 
we see that the complexity of the problem demands careful study and 
conservative action. 
2. MAN-MADE COMMUNITIES 
Animal communities are divisible into primeval or primary com- 
munities, and man-made, or secondary communities (12, 13). As has 
been noted when civilized man enters a new territory, he first destroys 
all large game which threatens himself and his domestic animals. He 
then destroys the natural vegetation and other animals by clearing the 
timber, burning all woody débris, and plowing and putting out plants 
which are entirely new to the region. Under primeval conditions, 
plants are arranged irregularly, as roughly indicated by the letters in 
Diagram 1; after being put to agricultural purposes, they are arranged as 
in Diagram 2. The plants are all of one kind and are arranged in rows. 
A grove of the original vegetation is sometimes left. The rate at 
which these changes take place is directly related to the rate at which 
man occupies and cultivates the new territory. As compared with 
natural changes, this process is rapid and is accompanied by an equally 
rapid decline of primeval or primary communities. 
