226 THE NATURAL HISTORY 



tenacious that it could by no means be cleared. The grapes 

 never filled to their natural perfection, but turned watery 

 and vapid. Upon perusing the works afterwards of M. de 

 Reaumur, I found this matter perfectly described and 

 accounted for. Those husky shells, which I had observed, 

 were no other than the female coccus, from whose sides this 

 cotton-like substance exudes, and serves as a covering and 

 security for their eggs." 



To this account I think proper to add, that, though the 

 female cocci are stationary, and seldom remove from the 

 place to which they stick, yet the male is a winged insect ; 

 and that the black dust which I saw was undoubtedly the 

 excrement of the females, which is eaten by ants as well as 

 flies. Though the utmost severity of our winter did not 

 destroy these insects, yet the attention of the gardener in a 

 summer or two has entirely relieved my vine from this 

 filthy annoyance. 



As we have remarked above that insects are often 

 conveyed from one country to another in a very unac- 

 countable manner, I shall here mention an emigration of 

 small aphides, which was observed in the village of 

 Selborne no longer ago than August the ist, 1785. 



At about three o'clock in the afternoon of that day, 

 which was very hot, the people of this village were 

 surprised by a shower of aphides, or smother-flies, which 

 fell in these parts. Those that were walking in the street 

 at that juncture found themselves covered with these 

 insects, which settled also on the hedges and gardens, 

 blackening all the vegetables where they alighted. My 

 annuals were discoloured with them, and the stalks of a 

 be(l of onions were quite coated over for six days after. 

 These armies were then, no doubt, in a state of emigration, 

 and shifting their quarters ; and might have come, as far 

 as we know, from the great hop-plantations of Kent or 

 Sussex, the wind being all that day in the easterly quarter. 

 They were observed at the same time in great clouds about 

 Farnham, and all along the vale from Farnham to Alton. 1 



1 For various methods by which several insects shift their quarters, 

 see Derham's Physico-Theology. 



