viii MAY-FLIES 313 



it rained several times during the morning and poured 

 all the afternoon. In the evening the Ephemerae 

 appeared at the usual time, though in smaller num- 

 bers, most of them having already emerged. Rain 

 was falling, though in less quantity. It appears, 

 therefore, that whatever the weather on the day of 

 emergence warm or cold, sunshine or rain the 

 Ephemerae quit the water at a fixed hour. 



" What becomes of the prodigious swarms of Insects 

 when they no longer fly through the air ? They are 

 for the most part already dead or dying. A large 

 part fall into the river from which they issued. The 

 Fishes enjoy a feast, and the Erench anglers speak of 

 the Ephemerae as manna e.g., they say the manna 

 has begun to appear ; there was a good fall of manna 

 last night. 



" Whether devoured by Fishes or not, those which 

 fall into the water soon perish. More lingering but 

 not less certain is the fate of those which descend 

 upon the banks or the neighbouring fields. Heaped 

 one upon another, and unable to move, they die by 

 inches, the last survivors perhaps seeing the rising of 

 the sun. 



" I returned to Paris on the 22nd at ten o'clock at 

 night, but left instructions to have the Ephemerae 

 watched on the following days. They appeared in 

 constantly diminishing numbers for four or five days 

 longer. 1 



1 Polymitarcys does not occur in the British Isles, though it 

 is plentiful in the large rivers of the Continent. I have seen 

 swarms of winged insects, rivalling those described by Reaumur, 

 at Dinant on the Meuse. 



