74 



INSECT TRANSFORMATIONS. 



of the raft. She proreeds in the same manner to add 

 eg^ after egg in a vertical (not a horizontal) position, 

 carefully regulating- the shape by her crossed logs; and 

 as her raft increases in magnitude, she pushes the 

 whole gradually to a greater distance, and when she 

 has about half-finished she uncrosses her legs and 

 places them parallel, the angle being no longer neces- 

 sary for shaping the boat. Each raft consists of 

 from two hundred and fifty to three hundred and 

 fifty eggs, which, when all laid, float on the water 

 secure from sinking, and are finally abandoned by 

 the mother. They are hatched in a few days, the 

 grubs issuing from the lower end; but the boat, now 

 composed of the empty shells, continues to float till it 

 is destroyed by the weather *. 



Gnats forming their egg boats, a, represents the commencement 

 of the boat of eggs; b, the boat about two-thirds completed; c, 

 the perfect boat resting ou the surface of the water. 



Kirby justly describes this little vessel as resembling 

 a London wherry, being sharp and higher, as sailors 

 f>ay, fore, and aft, convex below and concave above, and 

 always floating on its keel. " The most violent agita- 

 tion of the water," he adds, " cannot sink it, and what is 

 more extraordinary, and a property still a desideratum 

 in our life-boats, though hollow, it never becomes 



Reaumur, Me 



111. IV. p, 



G21. 



