NTRODUCTION 



1936 federal estimate found 128,429,000 people llvln 

 •^ er In the United States. Forty-four million four hundre 



^eighteen thousand hogs, 11,163,000 horses an 

 '387,251,000 chickens lived within our borders. Ou 

 country also had a population of multiplied trillion 

 of Insects. Some of these Interesting creatures are highly bene 

 flclal, others greatly hinder our progress. To successfully com 

 pete with them, we need to know the Insects better. 



This book Is designed to make It easy to acquire a read 

 knowledge of the Insects. It Is closely applicable throughou 

 North America and should be helpful wherever Insects are studied 

 Illustrated keys for Identifications of the orders and of th 

 principal families are given. One common representative of eac 

 included family Is pictured and briefly described. In all, IS 

 species of common Insects are thus treated. It should be born 

 In mind that for each species pictured, there are many other 

 which space does not permit us to show. When a specimen Is see 

 to closely resemble one that Is pictured. It will likely be foun 

 to belong to the same family. If It differs In some details 1 

 probably represents a species not herein described and will nee 

 to be referred to more complete literature or to a specialist 



Many small families of less common Insects do not appear 1 

 the keys. Had these been Included the keys would have become tc 

 cumbersome and difficult for beginners. As the student advance 

 in his study he will need to turn to special literature for thes 

 less frequent families. 



Reference has been made to many keys and descriptions by othe 

 authors. Many of the illustrations are original, others have bee 

 gathered from various sources by permission, recognition for whic 

 is indicated. Our students have made a large number of the drav\ 

 ings from specimens in the Iowa Survey Collection, tested the key 

 and helped in other ways. Valued suggestions by teachers v\^o ar 

 using the book in their classes have resulted in minor changes 1 

 the second, fourth and fifth printings. Space forbids any attemp 

 to name the many scientists and others who have helped. We wis 

 to thank them all. 



Mt. Pleasant, Iowa 

 March, 1939 



