104 FRESH WOODS. 



although insects of the air, go to the bottom 

 of the water to choose a place convenient to 

 lay their eggs, sacrificing thus their own lives 

 for the safety of their posterity. For the rest, 

 the ephemera does not gain much by its 

 maternal indifference, for it does not survive 

 the egg-laying, and the two sexes die always 

 very promptly when their role is finished." 



" This extreme brevity of life," continues 

 Pictet, is one of the characteristics of this 

 family which has most struck ancient ob- 

 servers, and it is worth saying a few words 

 about. In the ordinary state of things, the 

 same day, as Linnaeus says, includes for the 

 ephemera, its birth, its creation of a new 

 family, and its death ; often even half a day, 

 sometimes a few hours, suffice for that. 



In the summer days one sees these insects 

 shake off their envelope towards three o'clock 

 in the afternoon, fly upwards for a few hours, 

 couple, lay, and die when the sun disappears 

 below the horizon. Still, it is not necessary 

 to believe that this brevity of life is the result 

 of the organization of the ephemera. These 

 insects, and it is a fact already recognized by 

 M. de Geer, can be made to live many days, 

 and for that it is only necessary to prevent 

 reproduction. If at the moment of its birth 

 one takes an ephemera and shuts it up alone, 



