MOTIONS OF INSECTS. 367 



being observable in several others of the family, par- 

 ticularly in a still smaller fly with black pellucid wings 

 {jyiolohrusl) , and not uncommon in summer, whose 

 extremely rapid motion we have often admired as it 

 performs its minute gyrations on a leaf or the petal of 

 a flower. 



It was no less remarkable, that the two snowy- 

 winged gnats just mentioned were male and fe- 

 male, as the latter is seldom seen, and when the 

 males swarm upon a window, a single female can 

 scarcely be found; but though they were flirting 

 about on the same page, they took not the slightest 

 notice of one another, and each went through its 

 gyrations as if unconscious of the other's presence. 

 The female, besides, contrary to what is usual among 

 insects, was by far the most alert and agile of the 

 two; in so much that, though it was early in March, 

 we at first mistook her for the minute summer fly al- 

 luded to in last paragraph.* 



From all we have observed, we think it probable, 

 that notwithstanding the apparent sociality of the 

 dancing gnats {Tiimlidc'S),i\\Qy do not congregate 

 in consequence of any gregarious feelings, or for 

 mutual assistance; but merely because they are pro- 

 duced in numbers in the same places, and individually 

 prefer similar haunts. The individual sportive move- 

 ments of the two snowy-winged flies just described, 

 which were performed on the contiguous pages of a 

 book, or severally at the top and bottom of the same 

 page, prove that they do not consider the presence 

 of numbers indispensable. This position is farther 

 illustrated by the proceedings of an insect of a very 

 different family — the whirlwig beetles ( Gyrinidce, 

 Leach), which may be seen on the surface of every 

 pool weaving their eccentric dances, and twinkling 

 their polished corselets in the sun, both in summer 

 and, as we have remarked, throughout the winter. 



* J. R. 



