STUDY X. 67 



as the tip of the little finger, is produced from a 

 flu viatic grub, which is found particularly at the 

 mouths of rivers, clofe by the water's edge, in the 

 mud, into which it digs in queft of fubfiftence. 

 This grub lives three years, and at the termination 

 of that period, about Midfummer-day, it is trans- 

 formed, almoft inftantaneouily, into a fly, which 

 comes into the world at fix o'clock in the evening, 

 and dies about eleven at night. No longer fpace 

 of time is neceflary for copulation, and for de- 

 positing the eggs on the mud which the water 

 has deferted. 



It is very remarkable, that this infect copulates, 

 and lays her eggs, precifely at the time of the year 

 when the tides are at the loweft, when the rivers 

 difcover, at the place of their difcharge, the 

 greateft part of their channel dry. Wings are then 

 furnifhed, to enable her to go and dépolît her 

 eggs in places which the waters forfake, and to 

 extend, in the capacity of a fly, the domain of her 

 pofterity, at the time when, as a worm, her terri- 

 tory is mod contracted. I have likewife remarked, 

 in the microfcopic drawing and defections given 

 of this infed by the ingenious Thevenot, in the lafb 

 parts of his collection, that in her fly ftate, (lie 

 has neither interior nor exterior organs of nutri- 

 tion. They would have been entirely ufelefs to a 

 life of fuch tranfient duration. 



f 2 Nature 



