MOTIONS OP INSECTS. 371 



upon the earth or into the water, but not in conset 

 quence of being burned*. Reaumur was one of the 

 most accurate of observers ; and yet I suspect that 

 the appearance he describes was a visual deception, 

 and for the following reason. I was once walking in 

 the day-time with a friend ""j when our attention Wcis 

 caught by myriads of small flies, which were dancing 

 under every tree ; — viewed in a certain light they ap- 

 peared a concatenated series of insects (as Reaumur 

 has here described his Ephemerae) moving in a spiral 

 direction upwards ; — but each series, upon close exa- 

 mination, we found was produced by the astonishingly 

 rapid movement of a single fly. Indeed when we con- 

 sider the space that a fly will pass through in a second, 

 it is not wonderful that the eye should be unable to 

 trace its gradual progress, or that it should appear pre- 

 sent in the whole space at the same instant. The fly 

 we saw was a small male Ichneumon. 



Other circular motions of sportive insects take place, 

 in the waters. Linne, in his Lapland tour, noticed a 

 black Tipula which ran over the water, and turned 

 round like a Gyrinus*". This last insect I have often 

 mentioned ; — it seems the merriest and most agile of all 

 the inhabitants of the waves. Wonderful is the velocity 

 with which they turn round and round, as it were, pur- 

 suing each other in incessant circles, sometimes moving 

 in oblique, and indeed in every other direction. Now 

 and then they repose on the surface, as if fatigued with 

 their dances, and desirous of enjoying the full eflect of 



' Reaura. vi. 484. /. xlv. /. 7. 



'^ Th(? persona ()l>jerviitg tlic appearanre hcrf rolalcd were the author 

 i»f this work. " //OcA. Lapp. i. 104. 



^ B 2 



