THE GRASSHOPPER 17 



The visual organs comprise two compound eyes (Fig. 1) and 

 three simple eyes or ocelli. The compound eyes are built up of 

 hundreds of similar parts, each of which forms a portion of an 

 image and thus all together they produce a sort of mosaic. The 

 ocelli probably serve chiefly to distinguish light from darkness. 



The organs of touch, taste, and smell are represented by various 

 forms of bristles which usually lie in minute cavities and are 

 connected with the nervous system. Tactile or touch bristles 

 and often olfactory or smelling organs are located on the 

 antennae, whereas those concerned with taste are, as might be 

 expected, distributed over the mouth parts. 



The grasshopper has besides all these a pair of very interesting 

 auditory or hearing organs situated one on either side near the 

 forward end of the abdomen. They consist of a light membrane 

 so constructed as to vibrate, and receive and transmit sound 

 waves. These auditory organs enable the grasshoppers to 

 communicate with each other; thus the male Carolina locust 

 is often seen poising in the air with rapidly vibrating wings, and 

 making a crackling sound by rubbing the front and hind wings 

 together. 



Nervous System. — The stimuli received by the sense organs 

 are carried to the central nervous system by means of nerves, and 

 impulses are sent out by the central nervous system in the same 

 way. The insect in this manner becomes aware of the conditions 

 of its surroundings, and the impulses sent out result in appropriate 

 movements. The nervous system is essentially a double thread 

 united at intervals by a mass of nervous substance called a gan- 

 glion. The brain (Fig. 3, br) is the foremost mass of this sort. 

 From the brain one part of the double thread passes down on 

 either side of the oesophagus and unites below with another 

 ganglion (Fig. 3, soe. gl). Then follows a chain of eight gan- 

 glia lying near the lower part of the body in the median line. 

 Those in the thorax (Fig. 3, g. 2, g. 3) are the largest of these, 

 since they must control the wings and legs. The delicate 

 sympathetic nervous system (Fig. 3, asg, fg, Isg, psg, sgn) con- 



