34 NOTES ON 
the foot, and in the dry limb are barely per- 
ceptible, from its opacity ; as, however, in cast- 
ing the exuvie, these insects also throw off the 
covering of these hairs, they are exhibited in 
them with great effect. 
The transformation of the pupa to the per- 
fect fly is accomplished in the short space of a 
few minutes, and is an occurrence that is seldom 
observed. At the period of the change, it 
crawls out of the water, and fixes itself by its 
claws to some adjacent plant, and after remain- 
ing a few seconds it becomes dry, and the skin 
along the back separates, allowing the head and 
legs and part of the body of the perfect insect 
to be protruded, while the empty skin of the 
feet remains firmly fixed to the plant; it now 
