PREFACE. Vli 



orders, Kraepelin's careful analysis of the affinities of the 

 fleas appeared in 1884, and the year after Dr. F. Brauer's 

 " Systematisch-Zoologische Studien," in which he carefully 

 and yet boldly discusses the classification of insects, and 

 takes more analytical views than any of his predecessors. 

 Referring the Thysanura to a separate sub-class, Brauer 

 then, as we had previously done, divides the winged insects 

 into a number of super-orders, whose limits, however, differ 

 much from those assigned to the super-orders proposed by 

 us; yet we both agree as to the necessity of such groups. 



Brauer then proceeds to divide the winged insects into 

 sixteen orders, beginning, as we had done, with the ear- 

 wigs, Dermaptera, and ending with the Hymenoptera. He 

 regards the may-flies, the dragon-flies,' the stone-flies (Per- 

 lidae), the white ants and their allies, the Thripidae, the 

 forceps-tails, the caddis-flies, and the fleas as types of dis- 

 tinct orders. AVhen so able and sound a systematist arrives 

 at such conclusions, we feel emboldened to adopt them, 

 particularly as they coincide with our own maturer views. 



We have ventured to give the ordinal name Plectoptera 

 to the may-flies, and Mecaptera to the Panorpatae of Brauer, 

 but the credit of referring these types to distinct orders 

 belongs mainly to that eminent systematist. 



Although these changes in classification are based on our 

 increased knowledge of insects, it is also very convenient to 

 adopt a larger number of orders. There are probably about 

 a million species of ^nsects now existing, and it is unnatural 

 to crowd them into the old Linnaean orders. While the 

 Mollusks' (about 40,000 living species) are divided into twelve 

 orders, and the 5000 species of Crustacea into six; and while 

 the 10,000 species of living fishes are variously divided into 

 from six to fourteen orders, the class of reptiles into eleven 

 orders, the 7000 to 8000 species of existing birds into from 

 seven to eighteen orders, and the 3500 described living 

 species of mammals into fourteen orders, it seems not un- 

 reasonable to suppose that the number of insect orders is at 

 least proportionately as great. 



