286 INDIRECT BENEFITS DERIVED FROM INSECTS. 



covered in a few moments with these flies, which came 

 from all parts to overwhelm him. Before ten o'clock 

 this interesting spectacle had vanished. It was renewed 

 for some nights afterwards, but the flies were never in 

 such prodigious numbers. The fishermen allow only 

 three successive days for the great fall of the manna : 

 but a few flies appear both before and after, their num- 

 ber increasing in one case, in the other diminishing. 

 Whatever be the temperature of the atmosphere, whether 

 it be cold or hot, these flies invariably appear at the same 

 hour in the evening, that is, between a quarter and half- 

 past eight: towards nine they begin to fill the air; in 

 the following half-hour they are in the greatest num- 

 bers ; and at ten there are scarcely any to be seen. So 

 that in less than two hours this infinite host of flies emerge 

 from their parent stream, fill the air, perform their ap- 

 pointed work, and vanish. A very large proportion of 

 them falls into the river, when the fish have their grand 

 festival and the fishermen a good harvest a . 



Under this head I may observe how much the patient 

 angler is indebted to insects for some of his choicest 

 baits, for the best opportunities of showing his skill, and 

 for the most gratifying part of his diversion. The case- 

 worm and several other larvae are the best standing bait 

 for many fish. The larva of the Ephemera, there called 

 bait and bank-bait 5 , is much used in some parts of Hol- 

 land. The case-worms, and grubs (I suppose of flies) 

 from the tallow-chandlers are in request with us for 

 roach and dace ; and I am told by an acute observer of 



* Reaum. vi. 479-487. 



b Swamm. Bib. Nat. \. c. 4. 106. b. 



