64 INTRODUCTION. 



With such an extent of " sail-broad vans," it i9 

 easy for butterflies to support themselves for a long 

 time in the air; but their mode of flight, at least in 

 Reaumur's opinion, is generally not very graceful. 

 They seldom fly in a direct line, but advance by rising 

 and falling alternately, in a succession of zig-zags, up 

 and down, and from side to side. By flying in this 

 manner, they are supposed to elude more easily 

 the pursuit of the smaller birds, which often make 

 them a prey. " I one day watched with pleasure," 

 says Reaumur, " a sparrow pursuing a butterfly on 

 the wing for a considerable time, without succeed- 

 ing in catching it. The flight of the bird was not- 

 withstanding much more rapid than that of the but- 

 terfly, but the latter was always either above or be- 

 low the point to which the bird directed its flight, 

 and at which it expected to seize it." * Many of 

 the species, however, differ so much from each other 

 in their mode of flying, that a practised eye can re- 

 cognise them by this means alone. Such as are pro- 

 vided with strong wings, exercise a more steady and 

 continuous flight, nearly resembling that of a bird, 

 ascending high into the air, and often making their 

 way against a pretty strong current of wind. Of 

 our British species, the White Admiral is the most 

 celebrated for its manner of flying. " The graceful 

 elegance displayed by this charming species," says 

 Mr Haworth, " when sailing on the wing, is greater, 



* Reaumur, Memoires pour servir a VHistoire des In- 

 scctes, i. p. 203. 



