AUTHOR'S PREFACE xiii 



On account of the simultaneous use of older and newer names, 

 there is the awkwardness that one and the same insect appears in the 

 h'sts of visitors under different names; e.g., Anthophora pilipes F. and 

 Podah'rius acervorum L. Yet this inconvenience is minimized inasmuch 

 as at the end of the second volume there is given a systematic and 

 alphabetical list of the insects mentioned as visitors of flowers and the 

 flowers visited by them, with reference to the synonyms. The flower 

 visitors are mentioned in the alphabetical sequence of the orders, families, 

 genera, and species of insects, and at the same time both the older and 

 newer specific terms are given. 



In doubtful cases, where the correct name could not be determined, 

 the old name has been left ; thus, for instance, Limonius cylindricus Payk. 

 is mentioned by Hermann Muller as a visitor of Batrachium aquaticum. 

 This beetle may be L. nigripes F. or L. cylindricus L., but L. cylindricus 

 Payk. has been left. Similarly, Halictus albipes F. and H. longulus Sm. 

 are mentioned in the lists : both are certainly identical with H. calceatus 

 Scop., but are still considered as distinct by some investigators. Here 

 again, therefore, the old names have been left, the genus Halictus being 

 still in need of revision. 



In other cases, the names of visitors mentioned by a particular 

 observer are synonymous. For instance, Osmia aenea L. and O. caerulescens 

 L. are mentioned by the same writer as visitors of Lamium album. In 

 such a case the name (usually the older one) is chosen which is made 

 use of in the works on which modern nomenclature is founded. Names 

 of insects that are quite doubtful are omitted. 



Most of the illustrations are taken from the works of Hermann Muller ; 

 others are from the works of Darwin, Engler and Prantl, Hildebrand, 

 Kerner, Loew, MacLeod, Warming, and from my own earlier publications. 

 A considerable number have been made from nature for the handbook, 

 or have been drawn under my direction. 



The references to literature on the various groups and species of 

 plants are confined to the chief writings dealing with the plants in question. 

 A complete enumeration of all the works which refer to every species of 

 plant would have taken far too much space. Notices that are not referred 

 to in the text may in most cases be found by the use of the index to 

 the list of literature, which Dr. AppeP has drawn up in a most careful 

 manner. 



The abbreviations of references to literature used in the text are 

 usually self-explanatory ; in doubtful cases, the literature on flower pollina- 

 tion at the end of the first volume will give particulars. The following 



' Dr. Appel also helped me in reading the proofs, and prepared the greater part of the index 

 to the Introduction : for which favours I would here repeat my hearty thanks. 



