236 



THE INSECTS 



saliva and other juices, it passes in a fluid state through the walls of the 

 intestine, where it becomes part of the blood. As blood it is passed on 

 to tissues, such as muscle, to make new material to be used in repairing 

 that which is used up during the flight of the insect or to be oxidized to 

 release energy for the active insect. 



Eyes. — A considerable part of the surface of the head of the grass- 

 hopper is taken up by the compound eyes. Examination with a lens 

 shows the whole surface to be composed of tiny hexagonal spaces called 

 facets. Each facet is believed to be a single eye, with perhaps distinct 

 vision from its neighbor. The grasshopper also has three simple eyes on 

 the front of the head. The simple eyes probably are 

 only able to perceive light and darkness. The sepa- 

 rate units of the compound eye probably each give a 

 separate impression of light and color. Thus a com- 

 pound eye is most favorable for perceiving the move- 

 ment of objects. 



Other Sense Organs. — The segmented feelers, or 

 antennas, have to do with the sense of touch and smeU. 

 The eardrum, or tympanum, of the grasshopper is 

 found under the wing on the first segment of the ab- 

 domen. Covering the body and on the appendages, 

 are found hairs (sensory hairs) which appear to make 

 the insect sensitive to touch. Thus the armor-covered 

 animal is put in touch with its surroundings. 



Nervous System. — The nerve chain, as in the cray- 

 fish, is on the ventral side of the body. As in the 

 crayfish, it passes around the gullet near the head to 

 the dorsal side, where a collection of ganglia forms the brain. Nerves 

 leave the central system as outgoing fibers which bear motor impulses. 

 Other nerve fibers pass inward, and produce sensations. These are called 

 sensory fibers. 



Longitudinal section 

 of part of the com- 

 pound eye of an 

 insect : a, facets ; 

 c, nerves. 



Life History. — The female red-legged locust lays its eggs by 

 digging a hole in the ground with her ovipositor, or egg-layer, the 

 modified end of the abdomen. From twenty to thirty eggs are 

 laid in the fall; these hatch out in the spring as tiny wingless 

 grasshoppers, otherwise like the adult. As in the crayfish, the 

 young molt in order to grow larger, each grasshopper undergoing 

 several molts before reaching the adult state. No great change 

 in form occurs, the metamorphosis being said to be incomplete. 

 In the fall most of the adults die, only a few surviving the winter. 



Relatives of the Locust. — Among the near relatives are the 

 brown or black crickets, cockroaches and " waterbugs," the katydid, 



