116 TIIE BUTTERFLY VIVARIUM. 



lar facts concerning the Ephemeral common in the 

 Rhine. 



The broods described by Reaumur not only ap- 

 peared at a precise season but at a particular hour, 

 which was invariably between eight and ten o'clock 

 in the evening, at which time they filled the air in 

 vast multitudes, regardless of the state of the tem- 

 perature, or of wind or rain-storm. Their ap- 

 pearance and disappearance are both very sudden, 

 not a single individual being visible an hour before 

 or an hour afterwards. 



Other insects have also particular hours of pre- 

 ference, as it would seem, for the entrance upon 

 their most brilliant, but brief and final period of 

 existence. The Bornbyx of the Mulberry never 

 emerges from its chrysalis but at the hour of sun- 

 rise; the Lime Hawk-moth, Smerlnthus Tilice, at 

 midday ; the Death's-head Hawk-moth, Acherontia 

 Atropos, according to Schroeter, always making its 

 escape from the chrysalis betAveen four and seven 

 in the afternoon. But with regard to other kinds, 

 either they are altogether irregular in this respect, 

 or the observations of our naturalists have not 

 yet furnished us with a sufficient number of data 

 on the subject to enable us to decide the question. 



The method by which different insects escape 



