AUTHOR’S PREFACE Xili 
On account of the simultaneous use of older and newer names, 
there is the awkwardness that one and the same insect appears in the 
lists of visitors under different names; e.g., Anthophora pilipes F. and 
Podalirius acervorum Z. 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 Pays. 
is mentioned by Hermann Miiller as a visitor of Batrachium aquaticum. 
This beetle may be L. nigripes F. or L. cylindricus Z., but L. cylindricus 
Payk. has been left. Similarly, Halictus albipes 7. 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 Z. and O. caerulescens 
LZ. 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 Miiller ; 
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. Appel! 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. 
