VI PREFACE—Continued 
have adequately illustrated. The information that the collector 
needs first—size and distributional range—is made prominent 
in our account of each species. 
Owing to the insistence of other duties the completion of this 
book has been long delayed. Many of the pupils of the senior 
author have contributed materials for it. It is no longer possible 
to name them all, but the help of all 1s gratefully acknowledged. 
In the final putting together of these materials there are those 
who have aided so well and so generously as to deserve special 
mention. Mrs. H. E. Seemann assisted in the preparation 
of materials and drawings. Miss Elsie Broughton helped 
with the completion of both drawings and manuscript; and most 
of the drawings of genitalia were made by Mr. C. Francis 
Byers. Whole sections of the text have been written by the two 
last named. Dr. P. P. Calvert has very kindly read the galley 
proofs, and has helped with useful alterations and amend- 
ments. He has enabled us to eliminate some errors, but for 
such as may remain he is in no way responsible. 
It ts pleasant to be able to say at the end of this long-lagging 
task that we have met with only courtesy and help from all our 
scientific colleagues. During all these years peace and progress 
and good will have characterized the Odonatological Fraternity. 
JamMEsS G. NEEDHAM 
Hortense ButTteR HeEYwoop 
