CHAPTER XIX 

 THE COLEOPTERA 



The Coleoptera or beetles is the largest group of insects and members 

 of it are familiar to everyone. Over 175,000 kinds are already known, 

 and more are discovered every year. Beetles usually have wings, though 

 in some cases they are very small and never used. The front pair are 

 hard and horny and are called elytra. They are not used in flight but 

 when closed lie flat on the back, covering and protecting the hind wings 

 and the rather soft external skeleton of the upper side of the abdomen. 



FIG. 79. Water Beetle with wings spread. (From Folsom.} 



In some groups they do not reach the end of the body, and in those in- 

 sects the unprotected portion of the abdomen is generally of its usual 

 thickness. The hind wings are usually quite large and fold in an irregular 

 peculiar way to reduce their size and bring them under the elytra when 

 they are not in use (Fig. 79). 



The external skeleton of the beetles is usually harder and thicker 

 than in most of the other groups. The mouth parts are for chewing, 

 both as larvae and adults, and the jaws are often very powerful. The 

 early stages are entirely unlike the adult condition, the members of this 

 group undergoing a complete metamorphosis. 



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