64 
INTRODUCTION. 
With such an extent of “ sail-broad vans,” it is 
easy for butterflies to support themselves for a long 
time in the air ; hut their mode of flight, at least in 
Reaumur’s opinion, is generally not very graceful. 
They seldom fly in a direct line, hut advance by rising 
and falling alternately, in a succession of zig-zags, up 
and down, and from side to aide. 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," Bays 
Mr Haworth, “ when sailing on the wing, is greater, 
* Reaumur, Memoires pour servir a I'Histoire des In- 
teclet, i. p. 203. 
