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The three parts of the body of an insect are the head, the 
thorax and the abdomen. The first division of the body bears 
the antennae or "feelers" and the second division bears the 
legs and wings. The third division or abdomen is made up of 
a series of segments or "body-rings." The skeleton of an 
insect is external, that is, the body is supported and protected 
by a hard shell-like outer covering. This hard covering is 
called "chitin" and is so deposited in certain places as to form 
a hard and resisting surface, while in other places, it is flexi- 
ble enough to permit of a free movement of any one part or 
the movement of the body as a whole. This hard outer cover- 
ing of an insect is shed from time to time during the young, 
or developmental, period of the life of an insect. This process 
is called "moulting" and provides for increase in size or growth 
since the chitin is inflexible. 
The mouth-parts of an insect are of interest to the economic 
student of entomology for by determining the type of the 
mouth of any particular insect, we know the nature of the 
injury in the case of a plant-feeding species. The two impor- 
tant types of mouth are first, those which are formed for bit- 
ing - , and, second, those fitted for sucking. These are well 
illustrated by the slides. Insects possessing biting mouth- 
parts actually bite oft* or gnaw into, masticate and swallow the 
portions of the plant they feed upon. The mouth-parts of 
beetles and grasshoppers offer examples of this type. 
In such insects as leaf-hoppers, plant-life, and scale-insects, 
the mouth-parts are formed for piercing the tissues of plants 
and sucking therefrom the sap or juices. The portions of the 
plant fed upon are left intact but the result of the myriad of 
small pumps sucking out the very life of the plant, can be 
imagined. 
The organs of digestion consist of the alimentary canal and 
its appendages. The alimentary canal runs the entire length 
of the body in almost a direct line. It is separated into definite 
parts and supplied with various structures. The shape and 
size of the parts and the presence or absence of certain supple- 
mentary structures depends upon the feeding habits of the 
insect to a great extent. Necessarily the digestive system of 
a chewing insect that takes into its system portions of a plant 
would differ from that of a sucking insect that feeds upon juice 
or sap. 
All insects undergo during their life remarkable changes in 
form, structure and habits. With some, as the moths and 
butterflies, the change of form from the young to the adult 
stage is complete. These insects after hatching from the egg 
have three distinct stages or periods of development, that is, 
the young, or larval stage, known commonly as the cater- 
pillar, grub or maggot, during which time the insect takes 
the most food to provide for growth ; the pupa, a period dur- 
