iv PREFATORY NOTE. 



proposing such, the author has been actuated by a sincere desire to 

 simplify a confessedly intricate subject. 



In conclusion, he would desire to express his acknowledgments to 

 Dr. George H. Horn for the contribution of the articles on Hemip- 

 tera and Cantharis ; as well as to Professors Joseph Leidy, Ed- 

 ward D. Cope, and Horatio C. Wood, Jr., for assistance rendered 

 while the work was passing through the press. 



