CH. XIV.] EPHEMERA OR MAYFLY. 209 



tion between the two smaller ones being washed 

 away. These habitations are always made in a 

 soft soil ; but, should necessity force the insect to 

 provide a habitation in a coarser soil, it takes 

 especial care to protect its tender body by lining the 

 inside of its dwelling with fine earth. 



As the entrances to its dwelling are situated be- 

 low the surface of the water, the insect is surround- 

 ed by the element, and lives for two years in perfect 

 security within its retreat. With this, as with many 

 other insects, its house not only shelters, but feeds 

 it ; for it is easy to perceive through its transparent 

 body that its intestines are filled with the same earth 

 in which it has constructed its dwelling : it is proba- 

 ble that the soil is impregnated with some nutritious 

 substance which the insect's organization appropri- 

 ates After having sojourned within these dens for 

 nearly two years, and changed them as often as its 

 increase of bulk demanded a more spacious lodg- 

 ment, the insect undergoes those transformations 

 which permit it to enjoy in another element a mo- 

 mentary existence. 



Nevertheless, short as this term of life is, they are 

 surrounded at the very threshold of their new exist- 

 ence with the most imminent peril. The transform- 

 ation which is to convert the aquatic into the aerial 

 being is attended with all those risks which we have 

 seen attend the gnat : the ephemera is at the mercy 

 of a gust of air ; if once thrown off its balance while 

 endeavouring to extricate itself from its larval skin it 

 is lost for ever, for it has nothing to dread so much 

 as the element in which it has lived so long. When, 

 however, the insects have once become fitted for 

 their new mode of life, they burst at sunset from the 

 banks of the river which they have inhabited, in 

 such incredible numbers as to offer a spectacle 

 which can only be adequately described in the 

 words of Reaumur. " The cries of my gardener,' 

 says this naturalist, "attracted my attention to a 

 S2 



