274 Insects, 



and it seemed to be done for that very purpose. At all events, it had 

 that effect ; for after it had been twice or thrice repeated, it produced 

 a small longitudinal slit in the skin of the back of the fly. 



The slit, once produced, was speedily enlarged by continuing the 

 motion of the wings ; and the glossy chesnut back, beneath the ex- 

 ternal coat of a dull light brown colour, began to appear. The head 

 was now much depressed, and the back curved and elevated in an equal 

 degree ; the motion of the wings ceasing at the same instant. The 

 next part of the process seemed to be effected without difficulty or 

 exertion. The slit extended, and the body of the insect, beginning 

 with the highest part of the back between the wings, steadily emerged. 

 The wings themselves, still in their horizontal position, were gradu- 

 ally drawn back, so that their anterior edges formed a continually de- 

 creasing angle with the sides, and at last became parallel with them. 

 At this instant the head was freed, and raised aloft. Convulsive motions 

 of the body and tail ensued, and presently, wings and legs were all 

 released at once. 



But there yet remained to be performed what seemed to be the most 

 fatiguing and troublesome part of the operation, namely, the extrica- 

 tion and elongation of the whisks. Not one of these little Ephemerae, 

 previously to throwing off its envelope, had whisks exceeding \ of an 

 inch in length ; -^^ I should think, was about the length of those of 

 the majority. But after they had cast their skin, their whisks gene- 

 rally had been so much elongated as to measure \ an inch in length ; 

 and some even f : those of a very few retained their pristine dimen- 

 sions. As I have said, this part of the process was apparently more 

 difficult than that which had preceded it. It was certainly more te- 

 dious ; for in most cases it took up three or four times as much time, 

 and frequently, even more than that : and in not a few instances, it 

 was not completed at all, for the insect took flight with the husk still 

 attached to its setae. 



It was while the Ephemera was striving to extricate its whisks that 

 the benefit of having firmly fixed its feet to the substance which sup- 

 ported it (as above noticed) became apparent. All the force which 

 the little fly could use seemed brought into requisition. The whisks 

 were as unwilling to leave their sheaths, as an eel, in the hands of an 

 unpractised person, its skin. Their perfect extrication, therefore, de- 

 pended upon the skin of the feet retaining its hold : when it yielded, 

 the exuviae still adhered, and the flight of the insect was necessarily 

 much impeded ; for they all, without exception, took flight almost as 

 soon as the operation was over. From the first appearance of the slit 



