POSSIBILITIES AND COSTS. 67 



The compilation of a bibliography, including papers 

 produced in the domain of medicine, biology, insect clas- 

 sification, and economic entomolo2:v, is not the work of 

 a day nor the outcome of a simple searching in the in- 

 dex of one or a dozen standard authorities. Nor does 

 the mere enumeration of a list of the leading text books 

 suffice, for the bulk of the literature is found scattered 

 through the pages of the scientific periodicals of the last 

 twenty -five years. The " Zoological Record " and " Zoo- 

 logische Anzeiger" have been invaluable aids in this 

 work. It has been necessary to look carefully in books 

 and papers M'here the title afforded the least hope that 

 pei'tinent matter would be found. It was not, however, 

 alone difficult to compile this list on account of the scar- 

 city of works having reference to the subject, but it was 

 quite as perplexing to eliminate from the list those refer- 

 ences which were either duplicates or such as were con- 

 densed from more comprehensive productions. It may 

 be urged against this list that too much has been ex- 

 cluded, but, in order to make it of the greatest possible 

 worth to students, writings of the following classes have 

 been eliminated : — 



1. Pertaining to distribution, migration, and habits in 

 countries very remote from the United States. 



2. Abstracts of papers already published in more ac- 

 cessible form, or abstracts in languages not so generally 

 read as that in which the originals were published. 



3. Publications of a popular nature, in which the in- 

 formation is given at second hand, and not in such a 

 way as to make it as accessible as others of a similar 

 nature. 



4. Publications in languages such as Russian, Dutch, 



