GRASSHOPPERS AND CRICKETS . 
37 
work. The palpi feel about and locate the juicy parts 
of plants, the maxillae seize and hold them in position, 
while the hard mandibles tear the food into bits and 
pass it along to the digestive organs. 
Plants are able to build from mineral substances the 
materials which are useful food for the grasshopper, 
thus illustrating the well-known fact that without plants 
animals would die. Even animals which never eat 
plants subsist on other animals which depend on 
plant-food. As far as we know animals are unable to 
take nitrogen unless it has been previously made into 
plant-tissues which are suitable for animal food. 
Nutrition. It is not our purpose here to describe 
in detail the processes of nutrition in animals having 
so highly developed a digestive system as we find in 
the grasshopper. It is enough to say that the food 
passes through a long tube extending from the mouth 
to the anal opening at the posterior part of the body. 
This tube is often called the food-tube or alimentary 
canal. In the grasshopper and similar insects it 
is enlarged in one place to form a gizzard or grind¬ 
ing stomach. In some grasshoppers this gizzard is 
armed with teeth. There are also two other enlarge¬ 
ments known as the crop and the stomach. In its 
course through this tube the food is acted upon by 
fluids which soften it and change it chemically so that 
the nutritive portion is able to soak through the walls 
of the food-tube into the blood, which distributes it to 
all parts of the body, where it is used to build up tissue 
or to serve as fuel for heating the body. The portion 
of the food which is not so softened passes through the 
tube and is finally expelled from the body at the anal 
opening. 
Respiration. Taking Oxygen and Excreting Waste 
Substances, Food is useless to animals without a 
supply of air and an outlet for carbon dioxide, water, 
and urea. Man regularly inhales and expels air about 
eighteen times a minute. This process is so important 
