78 Miscellaneous. 



close to the surface of the water, whilst others rise to a greater height 

 in the air and even fly over the bridge. These are all males ; their 

 numbers gradually increase as evening approaches, when they force 

 themselves upon the notice even of the least observant. They appear 

 then in multitudes, and when at the approach of night the females 

 mix with them the crowds become still more dense, and the animals 

 settle by dozens on the clothes of the passengers on the bridge, and 

 the air appears as though snowflakes were whirling about in it in 

 every direction. At a later hour innumerable multitudes of these 

 Ephemerae may be seen dashing in circles round the lamps. What 

 takes place later in the night I know not, but in the morning we 

 often find the dead bodies of the animals lying heaped together in 

 prodigious quantities at the bottom of different houses situated close 

 to the Rhine. 



I have ascertained that these insects, which are rather nocturnal 

 than diurnal, stray to a considerable distance from the river, but only 

 single individuals, and these always males ; for this year, some days 

 after I had seen them on the bridge, I found single male specimens 

 in the " Hardt," a wood which is at some distance from the Rhine. 

 The spot where I took them was about three-quarters of a mile from 

 the town on the road which passes through this wood, so that by 

 this we know that the Ephemera exists at least that distance up the 

 stream ; but how much further its distribution may extend in that 

 direction, or to what distance down the river it may make its appear- 

 ance, is unknown. 



These appearances of large quantities of Ephemerae have long since 

 been noticed in Paris and Holland by Reaumur and Swammerdam. 

 The latter says, " Sometimes in Holland the sky suddenly becomes 

 darkened, as though covered with clouds, and this arises from an 

 innumerable quantity of Ephemerae which are produced all at once, 

 and which after death cover the shore, the ships and other objects, 

 forming sometimes a layer of an inch thick." Latreille, speaking of 

 the species described by Reaumur, says, " The fall of a species re- 

 markable for the whiteness of its wings produces the appearance of 

 one of those winter days when the snow descends in large flakes." 



Pictet was informed by DeCandoUe that on one occasion a small 

 Ephemera crowded into his house on the lake of Geneva, and that all 

 the furniture in the rooms in which lights were burning were covered 

 with a thick layer of them. 



One circumstance connected vdth this subject is interesting : each 

 of these diff'erent districts has its particular Ephemera. The insect 

 of the lake of Geneva (Ccenis lactea, Pict.) is not the same as that 

 which makes its appearance in Holland {Ephemera Svmmmerdamiana, 

 Lat.), whilst this again is distinct from that which rises from the 

 Seine in Paris {E. albipennis, Lat. ?) ; and lastly, the species which 

 inhabits the Rhine at this place differs from all the rest, and is as 

 yet undescribed, or at all events is not described in the most com- 

 prehensive works on these insects, — Pictet's Hist. Nat. des Ephe- 

 merines. 



Even the genus to which it belongs, although constituted by Pictet 

 under the name of Oliyoneuria, was but very imperfectly known to 



