Vlii PREFACE. 



So progressive a science as Zoology, and especially its sub- 

 division entomology, is in a transitory state, especially sys- 

 tematic entomology. We cannot, like the Chinese, actually 

 worship Linnaeus, our zoological Confucius; we cannot pay 

 too great deference to any system. Our ideas of classifica- 

 tion must change with our increasing knowledge. With the 

 evolution theory as a useful instrument of research, our 

 systems of classification representing what we suppose to be 

 the phylogeny of the class, we have a philosophical basis, 

 a working theory, which will throw light on dark places. 

 and solve many a knotty point. It is for this reason that 

 we need to study the embryology and life-history of insects, 

 supplementing these with anatomical investigations, besides 

 carrying on the work of collecting, describing, and thus en- 

 larging our knowledge of the distribution of insects in space 

 and time. 



The author gratefully acknowledges kind aid received 

 from several eminent naturalists in revising the portions 

 dealing with subjects of which they have a special knowl- 

 edge. Dr. P. E. Uhler has read the original MS. and proof 

 of the pages treating of the Hemiptera; Mr. Samuel Ilen- 

 shaw the same of the Coleoptera; and Dr. S. W. Williston 

 the pages devoted to the Diptera; while Prof essor Farlow 

 of Harvard University has kindly read the proof of the 

 section on Diseases of Insects due to Animal and Vegetable 

 Germs; Mr. N. N. Mason of Providence, R. I., has also 

 read the proof of Chapter VIII., and made some valuable 

 suggestions. 



Besides a number of cuts purchased of Prof. C. V. Riley, 

 which are acknowledged in the text. Figs. 87, 88, and 89 

 are taken from Darwin's Descent of Man (D. Appleton & 

 Co., New York); for electrotypes of several figures, from his 

 work on butterflies, I am indebted to S. II. Scudder, Esq.; 

 Fig. 238 was loaned by Prof. J. A. Lintner; Fig. 186 by 

 the U. S. Agricultural Department; and of Fig. S3 the 

 author was allowed the use by the Secretary of the Smith- 

 sonian Institution. A number of electrotypes from Judeich 



