THE ORDERS OF THE HEX A POD A. 47 



I. II. 



III. Orthoptera. \ Dekmaptera. {Forficulid^ 



( Orthoptera. 



IV. Physopoda. Physopoda. 



HOMOPTERA. 



V. Hemiptera. 



f Heteroptera. 

 f Neuroptera. {Sialida, Hemerobida.) 

 VI. Neuroptera. -j Mecaptera. (Panorpida.) 



I Trichoptera. (Phryganeida.) 

 VII. Lepidoptera. Lepidoptera. 



. TTTT _ S Diptera. 



VIII. Diptera. < „ ... ,. ., . 



( SlPHONAPTERA. (PltllCldce.) 



I Strepsiptera. (Stylopidw.) 



IX. Coleoptera. j Achreioptera. (Platypsyllida.) 



[Coleoptera. 



X. Hymenoptera. Hymenoptera. 



It is not my purpose in this place to discuss the distinguishing 

 features of the orders of insects. But it seems worth while to 

 present here a brief tabular statement of the more important ordinal 

 characters. This table will aid the student in formulating his ideas 

 as to the characters of the .orders and as to the relations of the 

 orders to each other. It should be borne in mind, however, that a 

 linear arrangement is not a natural one ; it is simply a necessity of 

 book-making. The arrangement adopted here is the one that I be- 

 lieve best indicates the relative rank of the various orders taken as 

 a whole. 



There is no doubt that the Thysanura is- the lowest of the orders. But the 

 position assigned to any one of the other orders is open to dispute. Thus we 

 find in the Orthoptera certain forms (the earwigs) which show as strong affini- 

 ties to the Thysanura as do any of the Pseudoneuroptera. And some entomol- 

 ogists hold that the Physopoda is the lowest of the orders of winged insects. 



To enter into a detailed discussion of the reasons which have led me to 

 adopt the sequence of the orders given in the following pages would be beyond 

 the scope of this work ; but the following generalizations will indicate the 

 more important ones. 



That series of orders in which the insects undergo an incomplete metamor- 

 phosis (the Ametabold) is undoubtedly lower than that (the Metabola) in which 

 the transformation is a complete one. The chief objection to placing the latter 

 series as a whole above the former is the wide separation thus brought about 

 between the Neuroptera and Pseudoneuroptera. I have felt, however, that 

 this was the least of two evils. Within the lower series the two orders in 

 which the mouth-parts are formed for biting are placed lower on this account 

 than the two orders in which the mouth is more highly modified. Of these 



