MOTIONS OF INSECTS. S71 
they appeared a concatenated series of insects (as Reau- 
mur has here described his Ephemera) moving in a 
spiral direction upwards ;—but each series, upon close 
examination, we found was produced by the ‘asto- 
nishingly rapid movement of a single fly. Indeed, when 
we consider 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 
present 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. Linné, 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 effect of 
the sun-beam: if you approach, they are instantaneously 
in motion again. Attempt to entrap them with your 
net, and they are under the water and dispersed in a 
moment. When the danger ceases they re-appear and 
resume their vagaries. Covered with lucid armour, 
when the sun shines they look like little dancing masses 
of silver or brilliant pearls °. 
But the motions of this kind to which I particularly 
ee Lapp. i. 194. 
b Compare Oliy. Entomol. iil, Gyrinus 4. 
O} 33 Ds 
