42 HISTORY OF 



transactions of its little life. It then may be said 

 to be in a hurry to live, as it has but so small a 

 time to exist. The peculiar sign whereby to 

 know that these reptiles will change into flies in 

 a short time, consists in a protuberance of the 

 wings on the back. About that time the smooth 

 and depressed form of the upper part of the 

 body is changed into a more swoln and rounder 

 shape, so that the wings are in some degree visi- 

 ble through the external sheath that covers them. 

 As they are not natives of England, he who would 

 see them in their greatest abundance must walk, 

 about sun-set, along the banks of the Rhine, or 

 the Seine, near Paris; where, for about three 

 days in the midst of summer, he will be astonish- 

 ed at their numbers and assiduity. The thickest 

 descent of the flakes of snow in winter seems not 

 to equal their number ; the whole air seems alive 

 with the new-born race, and the earth itself is all 

 over covered with their remains. The aurelias, 

 or reptile insects, that are as yet beneath the 

 surface of the water, wait only for the approach 

 of evening to begin their transformation. The 

 most industrious shake off their old garments 

 about eight o'clock ; and those who are the most 

 tardy, are transformed before nine. 



We have already seen that the operation of 

 change in other insects is laborious and painful ; 

 but with these nothing seems shorter, or per- 

 formed with greater ease. The aurelias are 

 scarcely lifted above the surface of the water be- 

 fore their old sheathing skin bursts ; and through 

 the cavity which is thus formed, a fly issues, 



