TRANSACTIONS 



OP 



THE LINNEAN SOCIETY. 



I. A Bevisional Monograj^h of decent Bpliemeridce or Ilayjllcs. By the Bev. A. E. 

 Eaton, M.A. {Commimicated by Sir John Lubbock, Bart,, F.B.S., Pres. Limi. Soc.) 



(Plates I.-LXV.) 



Part I. Read April 10th, 1883. 



Inteoductort Eemaeks. 

 I HE present monograph is designed to facilitate the study of the Ephemeridte. On 

 many accounts these insects are very eligible subjects for scientific research ; but so long 

 as they are Ul known, and their exact identification a matter difficult of accomplish- 

 ment, their employment in any branch of zoological learning is surrounded with dis- 

 advantages too patent to need indication. 



Many points in the classification of the Ephemeridaj formerly doubtful receive 

 elucidation in this work through the kind co-operation of entomologists of various 

 nationality. An unprecedented wealth of material, through their means, has been 

 avaUable for examination, every thing at their disposal likely to be in any way of 

 service to me having been most courteously given or lent by them. The chief con- 

 tributors of specimens have been Mr. E,. M^Lachlan, F.R.S., and Dr. H. A. Hagen, of 

 Cambridge, Mass. I am also under great obligations to Mr. H. Albarda of Leeuwarden, 

 Mr. C. Ritsema of Leyden, the Baron E. de Selys-Longchamps, M. Albert Mtiller of 

 Berne, M. A. E. Vayssiere of Marseilles, and Dr. E. Joly of Toulouse. My thanks are 

 also due respectively to the chief Entomologists or Directors of the British, Oxford, 

 Brussels, Paris (Jardin des Plautes), and other museums, for permitting valuable 

 specimens to be thoroughly examined by me. Many very choice Ephemerida; in the 

 Museum of Comparative Zoology, Cambridge, Mass., forwarded by Dr. Hagen, and some 

 remarkable species contributed by Mr. O. Salvin, demand particular acknowledgment. 



At an initial stage in the preparation of the letterpress, having decided to write in 

 English, the question arose whether or not descriptions of the species should be given, or 

 should the text treat of genera only. The various tints of yellow, brown, grey, and, in a 

 lesser degree, of black, largely prevalent in the coloration of Ephemeridae, cannot be 

 precisely defined in common English entomological terms so well as in Latin ; and 



SECOND SERIES. — ZOOLOGY, VOL. III. 1 



