EPHEMERAE. 



213 



are produced from larvae which inhabit the 

 water, which can both crawl and swim, and 

 which generally live in holes they make in 

 the bottom. They change their coats seve- 

 ral times before they become nymphae. They 

 quit their skin on the surface of the water, 

 but even after they become flies, they have 

 another transformation to undergo before 

 they are perfect animals fitted for generation. 

 They make use of their wings only to fly to 

 some dry bank, or trunk of a tree, where 

 they gradually disencumber themselves of 

 the whole of the outward habiliment they 

 brought from the water, including their 

 wings. They become lighter, more beauti- 

 ful in colour, and then begin their sports in 

 the sunshine— appearing like what might be 

 imagined of spirits freed from the weight of 

 their terrestrial covering. This last trans- 

 mutation has been observed and fully de- 

 scribed by some celebrated naturalists, in 

 the case of the May flies, and one or two 

 other species, and it probably will be found 

 a general circumstance attached to the class, 

 and I have often observed what appeared to 



