VIII MAY-FLIES 303 



of the body, and the short duration of the winged 

 Insect. After emergence they do not Hve more than 

 five hours at the most, that is from six or half past 

 six in the evening to eleven. I have observed the 

 length of their duration in the winged state by keep- 

 ing the winged Insects in a box. 



"Vast numbers perish at the moment of their 

 emergence, being devoured by Fishes. Those which 

 escape from the water are devoured in large numbers 

 by Swallows and other Birds. If they escape this 

 peril, and return to the surface of the water, many 

 fall a prey to Fishes. At the time when the winged 

 Palingenia abounds, it has been observed that the 

 Trout are fatter and better flavoured. 



" It is well known to all persons who frequent 

 rivers, that the Ephemerae appear in continual suc- 

 cession for three days. A few may be seen on the 

 fourth or even on the fifth day. 



"What I have related concerning Palingenia 

 differs in many particulars from the account given 

 by Mouffet, Aldrovandus, Johnston, Clutius and 

 others, but I am far from judging or blaming them. 

 It may easily be that these naturalists have described 

 a different species from mine, but I would recommend 

 every one who desires to know the truth about these 

 things to learn himself of Nature, for Nature can 

 teach in a short space of time more than any one can 

 learn in a long course of years from many books. 



" While studying the life-history of Palingenia, I 

 became acquainted with other species. None of these 

 live so short a time in the winged state as Palingenia. 

 In the month of June 1670, at Sloten near Amsterdam, 



