PREFACE. IX 



The foregoing was written some years ago. In 1865 the 

 manuscript of the memoir was sent to the Smithsonian Institu- 

 tion. 



Its publication was at first delayed by the pressure of other 

 matter, then by an unfortunate fire which embarrassed the finances 

 of the Institution, and lastly the slow delays below mentioned. 



The book has been in the press several years, in consequence 

 of the great loss of time caused by the transmission of the proofs 

 from Europe to America, and vice versa. 



In consequence of this long period of waiting, I have been 

 obliged to make a review of the manuscript in reference to the 

 writings of various entomologists, especially those of Mr. Cresson, 

 which have been published from year to year, and have changed 

 the names of the species which I had described and have adopted 

 the names given by this author. I have not been able, however, 

 to take account of the more recent writings of Mr. Cresson, on 

 the Hymenoptera of Texas, which only came to my knowledge 

 when the printing of this book was almost finished. 



The reader will excuse certain irregularities, consequent upon 

 the difficulty of putting a work into perfect symmetry which was 

 to be printed on the other side of the Atlantic. Hence the author 

 has never had but a part of his work before his eyes at a time. 

 during the long course of this publication. For example, it will 

 be noticed in the synonymy that my work, "Etudes sur la Famille 

 des Vespides" is sometimes cited " Et. Yesp.," sometimes only 

 "Vespides." So with the "Revue et Magazine do Zoologie," it 

 is sometimes cited "Rev. et Mag. de Zoolog.," and sometimes 

 simply "Rev. de Zool." 



The larger part of the book was written in French, and has 

 been translated and corrected by Mr. Edward Norton. I owe 

 to this naturalist also various communications and frequent stand- 

 ings of insects, which have been of great use to me. 



H. De SAUSSURE. 



