38 BEST'S ART OF ANGLING. 



observing them, I could tell when they were 

 ready to put off their husks, though but so lately 

 put on. I had the pleasure to show my friends 

 one that I held in my hand all the while it per- 

 formed this great work. It is surprising to see 

 how easily the back part of the fly split open,, and 

 produced the new birth, which 1 could not per- 

 ceive partakes of any thing from its parent, but 

 leaves head, body, wings, legs, and even its 

 three-haired tail, behind on the case. After it 

 has reposed itself a while, it flies with great 

 briskness to seek its mate. In the new fly a 

 remarkable difference is seen in their sexes, 

 which I could not so easily perceive in their first 

 state, the male and female being then much of a 

 size ; but now the male was much the smallest, 

 and the hairs in his tail much the longest. I was 

 very careful to see if I could find them engender- 

 ing, but all that I could discover was, that the 

 males separated, and kept under cover of the 

 trees, remote from the river : hither the females 

 resorted, and mixed with them in their flight, 

 great numbers together, with a very quick mo- 

 tion of darting or striking at one another when 

 they met, with great vigour, just as house-flies 

 will do in a sunny room : this they continued to 

 do for many hours, and this seemed to be their 

 way of coition, which must be quick and soon 

 performed, as they are of so short a duration. 

 When the females were impregnated, they left 

 the company of the males, and sought the river, 

 and kept constantly playing up and down on the 

 water. It was very plainly seen, that every time 

 they darted down, they ejected a cluster of eggs, 

 which seemed a pale, blueish speck, like a small 

 drop of milk, as they descended on the water; 



