THE DAY FLY. 4*5 
like thofe of fakes, and probably deftined to ferve the 
fame purpofe. 
They are feen arranged along each fide of the abdo- 
men, one on every fegment, from the fint to the fixth or 
feventh. When the infect is at reft, thefe branchiae are 
feen moving with great rapidity ; and from their peti- 
tion, Reaumur has diftributed the chryfalids of ephemerte 
into three difttnet claffes *. 
Some of thefe chryfalids walk or fwim up and down 
in the water, attach themfelves to plants, or conceal 
themfelves beiovv the ft ones : Others have the firft pair 
of fest formed for digging into the ground, and befides, 
are provided with two inftruments on the forehead, ftill 
better adapted to that purpofe : with thefe, each animal 
digs itfeif a hole on the river b mk, wh re it conf'antly 
refides. The brinks of the Marne and the Seine in France 
ate feen thickly perforated by thefe animals : The holes 
thus excavated are generally nearly on a level with the 
furface of the water, and have commonly two apertures ; 
one oy which the worm enters, and another by which it 
returns. 
Thefe animals, while they remain in thefe fubterrane- 
ous retreats, offer but few materials to the natuialift who 
would record their hittory : Though many Oi them remain 
there for two years, and feed upon the earth in which 
they are lodged, yet they are effe&ually concealed during 
all that period from his oblcrvation. Probably the moft 
interefting incidents oi their lives are thofe which happen 
in our view, and are confined to the narrow fpace of a 
few hours. Their (lory becomes then eventful ; for in 
that 111 or t period they are transformed into flies, the fe- 
3 O 2 1 male^ 
f Tome VI. room. it. 
