392 THE HOP CHOP. 



vian guano, will assist them much when they begin to 

 grow again. 



The great destroyer of the hop grounds, however, is 

 the Aphis humuli, or "hop -fly/' which makes its 



1 and 2. Female Aphis, natural size and magnified. 3 and 4. "Nits" of do., natural size 

 and magnified. 



appearance about the middle or end of May, when, 

 the bine has made a growth of 4 to 5 feet up the 

 poles. Like other aphides, it is first seen at the top of the 

 plant, fixing itself on the under side of the leaves next 

 to the head, and there propagating itself after the rate 

 already described at p. 234, vol. i. The visits of these 

 insects to our crops are still invested with a sort of mys- 

 tery. We know but little of the conditions, whether of the 

 plant or of the season, that cause them to come, or that 

 relieve us from their presence ; their increase is irregular, 

 sometimes very rapid, at others far less so, and in some 

 seasons a change in the wind will cause them to disappear 

 even more rapidly than they appeared. They appear 

 to be particularly susceptible of atmospheric influences, a 

 favourable change in the weather often, saving the crop from 

 impending destruction. In June, 1846, Mr. Paine tells 

 us the hops in the Farnham district were seriously infested 

 by this insect, from which they were suddenly freed, and 

 afterwards produced the largest crop ever known in that 

 quarter. The condition of the plant, therefore, is never 



