INDIRECT BENEFITS DERIVED FROM INSECTS. 163 



beginning to quit their slough, others prepared to fly, and others already on 

 the wing ; and every where under the water they were to be seen in 

 a greater or less degree of forwardness. The storm coming on, he was 

 obliged to quit the amusing scene ; but when the rain ceased to fall, he 

 returned to it. As soon as the cloth with which he had ordered the tub 

 to be covered was removed, the number of flies appeared to be greatly 

 augmented, and kept continually increasing ; many flew away, but more 

 were drowned. Those already transformed, and continually transforming, 

 would have been sufficient of themselves to have made the tub seem full ; 

 but their number was soon very much enlarged by others attracted by the 

 light. To prevent their being drowned, he caused the tub to be again 

 covered with the cloth ; and over it he held the light, which was soon 

 concealed by a layer of these flies, that might have been taken by handfuls 

 from the candlestick. 



But the scene round the tub was nothing to be compared with the 

 wonderful spectacle exhibited on the banks of the river. The excla- 

 mations of his gardener drew the illustrious naturalist thither ; and such 

 a sight he had never witnessed, and could scarcely find words to describe. 

 " The myriads of Ephemerae," says he, " which filled the air over the 

 current of the river, and over the bank on which I stood, are neither to 

 be expressed nor conceived. When the-snow falls with the largest flakes, 

 and with the least interval between them, the air is not so full of them as 

 that which surrounded us was of Ephemerae. Scarcely had I remained in 

 one place a few minutes, when the step on which I stood was quite con- 

 cealed with a layer of them from two to four inches in depth. Near the 

 lowest step a surface of water of five or six feet dimensions every way was 

 entirely and thickly covered by them ; and what the current carried off 

 was continually replaced. Many times I was obliged to abandon my 

 station, not being able to bear the shower of Ephemerae, which, falling 

 with an obliquity less constant than that of an ordinary shower, struck 

 continually, and in a manner extremely uncomfortable, every part of my 

 face eyes, mouth, and nostrils were filled with them." To hold the 

 flambeau on this occasion was no pleasant office. The person who filled 

 it had his clothes 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 number 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 numbers ; 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 appointed work, and vanish. A very 

 large proportion of them falls into the river, where the fish have their 

 grand festival and the fishermen a good harvest. 1 



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 



1 Reaum. vi. 479 487. 

 M 2 



