546 Missouri Agricidtural Report. 



but every observer knows that song birds are becoming less nu- 

 merous every year and that destructive insects are becoming more 

 numerous. 



But insects are not alone in levying a tax on agriculture. Such 

 rodents as rats, mice and gophers also exact a tribute, and although 

 the total is not as large as is exacted by our insect enemies, it 

 amounts, on the whole, to millions of dollars every year. These 

 also increase and become troublesome as a direct result of the 

 destruction of their natural enemies. To begin with, the various 

 species of animal life were well balanced and one species prevented 

 the overproduction of another. When man interfered and re- 

 moved one, those which had furnished it with food immediately be- 

 came more numerous and in many cases have caused untold injury. 

 The introduction of any old world animal, bird or insect is likely 

 to be attended with serious consequences because their natural 

 enemies are seldom brought also. 



Birds play an important part in reducing the number of weed 

 seeds as well as noxious insects, and such animal pests as mice, 

 rats, moles, etc. The part played by certain small animals, such as 

 weasels and skunks, is also worthy of some attention. As a 

 naturalist, the writer has occupied much time in the study of 

 economic aspects of animal and bird life. Hawks have been 

 watched for weeks to ascertain on what they were feeding ; skunks 

 and weasels have been encouraged to live about the place that they 

 might be observed also. Some of these observations are recorded 

 in this paper. 



Most insects pass through four different stages during life. 

 The first stage is that of the egg, the second stage the larvae or 

 worm stage. It is in this stage that most of the growth is made. 

 The little larvae is very minute when first hatched, but grows 

 very rapidly and moults or sheds its skin frequently until it com- 

 pletes its growth. A remarkable change now takes place. The 

 insect becomes quiet and becomes encased, as a rule, in a sort of 

 casket. No food is taken and it is helpless to move about. This 

 third stage is called the pupa. Many of the moths pass this stage 

 within a silken cocoon, and later emerge as mature insects. 



There are exceptions to this four stage life history, however. 

 Moths, butterflies, bees, beetles and many others pass through the 

 four stages which are known as the complete metamorphosis. 

 Grasshoppers, crickets and cockroaches hatch from the eggs in 

 the same form as the adults, and are known as nymphs. They con- 

 tinue to moult frequently until they complete their growth, but at 



