160 



Elementary Principles of Agriculture 



230a. Structure of Insects. For this exercise the pupil should 

 secure good specimens of the grasshopper and butterfly, as these 

 two insects illustrate the difference of mouth parts as seen in insects. 

 Some, as the grasshopper, have biting mouth parts, while others, 

 as the butterfly, squash bug, etc., have mouth parts suited to pierce 

 the plants and suck out their juices, (a) Note the large eyes in the 

 front and side of the head of each insect. These are called com- 

 pound eyes because they are made up of a great number of simple 

 eyes. (6) Note also the feelers or antennae, and the mouth parts. 

 The large black jaws of the grasshopper are used for biting, while 

 the long coiled tongue-like organ of the butterfly is used for obtain- 

 ing food by sucking out the nectar from flowers. 



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Fig. 100. San Jose scale on plum. A, natural size; b, magnified; 

 c, greatly magnified. 



230b. The next region of the body is called the thorax. In each 

 insect the thorax is divided into three parts, each division has a 

 pair of legs attached. All insects have six legs, and are sometimes 

 called Hexapoda on this account. On each insect you will find two 

 pairs of wings. These wings are attached to the second and third 

 divisions of the thorax. Notice that the wing of the butterfly is 

 covered with a "powder." This powder is made up of small scales 

 attached to the wing in rows overlapping each other very much 

 like the shingles of a roof. The wing of the grasshopper is smooth 

 and firm with a large number of small lines running through it, 

 called veins. 



230c. The next division of the body is called the abdomen, 

 which is made up of a number of segments or rings. By looking 

 along the side of the abdomen of the grasshopper there will be seen 

 a number of small openings or pores. These are the breathing pores 



