MIGRATIONS OF INSECTS. 269 



to be noticed with surprise by the most incurious ob- 

 servers.'* 



We confess we feel not a little disappointed that 

 the species is not mentioned in these instances, as it 

 might serve to fill up a blank in the history of some 

 of those which are most destructive. In the case of 

 the hop-fly, we have remarked for several successive 

 years, that soon after Midsummer they all disappear, 

 though the leaves have only a few days before been 

 literally covered with them in millions. The same is 

 the case with those called the dolphin, which infest 

 the bean {Aphis fabce), and that named the zebra 

 {A. sambuci.) It is highly probable that all these 

 perish soon after the deposition of the eggs for the 

 succeeding spring ; but it is by no means an easy 

 matter to ascertain this. If they migrate to the sea- 

 coast and are drowned, as we are partly entitled, from 

 the statements just given, to infer, their fate is similar 

 to another still more destructive insect, the locust 

 (Locusta migratoria, Leach.) f 



The prophet Joel, who has given so striking a 

 picture of the devastation produced by locusts, J has 

 not forgotten to notice their destruction, when he 

 says, ' I will remove far off from you the northern 

 army, and will drive him into a land barren and 

 desolate, with his face toward the east sea, and his 

 hinder part toward the utmost sea, and his stink 

 shall come up, and his ill-savour shall come up be- 

 cause he hath done great things.' § Mr Barrow 

 tells us, that in Southern Africa, in 1784 and 1797, 

 they covered, during their progress, an area of nearly 

 two thousand square miles, but were ultimately driven 

 into the sea by a north-west wind, where they formed 

 upon a shore, for fifty miles, a bank three or four 

 feet high, and when the wind was south-east their 



* Intr. ii, 9. t See Insect Transformations, p. 251. 



t Ibid, p. 246. § Joel, chap, ii, 20. 



VOL. XII. 23* 



