The Classitication of Insects 53 



mology recognizes nineteen distinct ones. This does not mean, of course, that 

 twelve new orders of insects have been found since Linnius's time, although 

 two or three of the orders are in fact founded on insects unknown to him, 

 but means that certain small groups classified by Linnsus simply as families 

 in his large orders have been given the rank of distinct orders by modern 

 systematists. And as our knowledge of insects and their relationship to 

 each other is certainly much larger now than it was one hundred and fifty 

 years ago, we may feel confident that the many-order system of classifica- 

 tion is more nearly a true expression of the natural interrelationships of 

 insects than was the old seven-order system. But not all entomologists 

 agree on the nineteen-order system. Few, indeed, still use the Linna;an 

 system, but many believe that the division of the insect class into nineteen 

 orders gives too much importance to certain very small groups and to some 

 others which are not markedly aberrant, and these entomologists recognize 

 a lesser number of orders, varying with different authors from nine to about 

 a dozen. In this book we shall adopt the nineteen-order system as used 

 in Comstock's Manual. In the first place the author believes that this classi- 

 fication best represents our present knowledge of insect taxonomy; in the 

 second place this is the classification taught by nearly all the teachers of 

 entomology in America. 



To determine the order to which an insect belongs we make use of a 

 classifying table or key. In the Key to Orders which follows this para- 

 graph, all the insect orders are characterized by means of brief statements of 

 structural features more or less readily recognized by simple inspection of 

 the superficies of the body; to determine some of the conditions a simple 

 lens or hand-magnifier will be needed. The orders are so arranged in the 

 key that by choosing among two or more contrasting statements the student 

 may "trace" his specimen to its proper order. Inspection of the Key with 

 an attempt or two at tracing some familiar insect, as a house-fly, moth, or 

 wasp whose order is already known, will make the method of use apparent. 

 It must be borne in mind that young insects, such as caterpillars of moths, 

 grubs of beetles, and the wingless nymphs of locusts, dragon-flies, etc., cannot 

 be classified by this key. Indeed the young stages of most of the insects 

 which we know well as adults are unknown to us, and there is, besides, such 

 manifold adaptive variety in the external structure of those forms which we 

 do know that no key for the classification into orders of immature insects 

 can now be made. 



