THE DAY FLY. 475 



like thofe of fifhes, and probably deflined to ferve the 

 fame purpofe. 



They are feen arranged along each fide of the abdo- 

 jnen, one on every fegment, from the firlt to the fixth or 

 feventh. When the infe£l is ai reft, ihefe branchiae are 

 feen moving with great rapidity j and from their pofi- 

 tion, Reatonur has diftributed the chryfalids of ephemerae 

 into three diftind; clalTes *. 



Some of thefe chryfalids walk or fwim up and down 

 in the water, attach themfelves to plants, or conceal 

 themfelves below the ft mes : Others have the firft ^air 

 of feet :ormed for digging into the ground, and befides, 

 are provided with two inltruments on the forehead, ftill 

 better adapted to that purpofe: with thefe, each aniaial 

 digs itfeif a hole on the river bc;nk, wh-re it conftantly 

 refides. The brinks of the Marne and the Seine in France 

 are feen thickly perforated by thefe anim -is : The holes 

 thus excavated are generally neai'ly on a level with the 

 furface of the water, and have commonly two apertures ; 

 one by which the worm enters, and another by which it 

 returns. 



Thefe animals, while they remain in thefe fubtcrrane- 

 ous retreats, offer but few materials to the naturalift who 

 would record their hiltory : Though many oi them remain 

 there for two years, and feed upon the earth in which 

 they are lodged, yet they are efFedtually concealed during 

 all that period fpm his oblervation. Probably the moft 

 interefting incidents oi.tiieir lives are thofe which happen 

 in our view, and are confined to the narrow fpace of a 

 few hours. Their llory becomes then eventful ; for in. 

 that fhort period they arc transfornjed into flies, the fe- 

 3 O 2 jnale? 



* Tomt VI. mem. i?. 



