On issuing the third and final part of the Index, we wish to return our thanks to 

 Mr. Sereno Watson for aid in determining the names of host-plants, to Dr. George 

 Vasey for the revision of the names of the grasses ; and to Prof. Roland Thaxter for 

 a revision of the list of fungi on insects. We also would acknowledge with thanks 

 information with regard to synonymy and corrections kindly furnished by Mr. J. B. 

 Ellis, Dr. O. Pazschke, Prof. C. H. Peck, and Mr. W. T. Swingle. 



The general plan of the Index was sufficiently set forth in the preface of Part I, 

 and it only remains to state the plan pursued in the Addenda. Where species are 

 introduced either as new to this Index, or as occurring on hosts not recorded in the 

 body of the Index, they are printed in common type. Where new varieties of spe- 

 cies previously given are introduced, the varietal name only is given in common 

 type, the specific name being in italics. Where the new names are synonymous with 

 names given previously in the Index, they are placed in braces with one or more of 

 the names previously given, the latter being printed in italics. Some of the species 

 before reported are now known either to have been incorrectly determined or not to 

 occur on the hosts originally given, and these facts have been brought out :is 

 far as possible by the synonymy or by the use of the words "species excludenda." 

 As before, the arrangement of synonyms in braces is chronological and, in using the 

 Index, it should not be forgotten that unpublished names are not given except in a 

 few cases where necessary to avoid confusion of synonymy. 



W. G. FARLOW. 

 Cambridge, June /j , 1891. 



