PREFACE. 



The present work was prepared for press some years ago^ but 

 its publication has been delayed pending the appearance of my 

 Revision of the LibeUulince in the ' Transactions of the Zoological 

 Society of London/ which was not issued till last year. 



Comparatively few recent species of the suborder Odonata 

 are known at present — about 1800, or rather more than half 

 as many as those belonging to the least numerous Classes of 

 Vertchrata, such as Mammalia or Reptilia ; and very much fewer 

 than those of the larger families of such Orders of Insects as 

 Coleojjtera or Lepidoptera. But the Dragonflies have hitherto 

 met with but little attention, being a group of insects which are 

 very brittle, occupy much space in cabiuets, and are very liable 

 to lose their colours. 



The tendency of all Catalogues and Monographs is to render 

 themselves incomplete; and I have little doubt that the number 

 of species of Odonata now known could easily be at least 

 quadrupled if more workers were attracted to the subject ; for 

 the present Catalogue (except in the subfamilies LihelluUnts 

 and jEschninoi) is mainly a record of the work of one or two 

 writers oidy, — notably that of the veteran Belgian entomologist 

 Baron E. de Selys-Longchamps, who has devoted a great part 

 of his long life to the study of Odonata, and has monographed 

 all the subfamilies (except the two above-mentioned), aided by 

 the constant advice and assistance of Dr. Hagen, to whom all 

 entomologists are so deeply indebted for his invaluable ' Biblio- 

 theca Entomologica.^ It is to be hoped that the Baron will 



