CULTURE AND PRODUCTION IN ENGLAND. 59 



hops is placed in a sulphuretted hydrogen apparatus, with 

 some zinc and hydrochloric acid; the disengaged gas is 

 passed through a solution of acetate of lead. 



If the hops contain sulphurous acid, sulphuretted hydrogen 



will be disengaged : 



(S0 2 +2H 2 +2H 2 0), 



and black sulphide of lead thrown down from the lead solu- 

 tion. Better still is to receive the disengaged gas in a 

 solution of nitroprusside of sodium, to which a few drops 

 of potash ley have been added; the slightest trace of sul- 

 phuretted hydrogen imparts a beautiful purple red colour to 

 the solution. (Wagner.) 



Insect Depredators. Although incidental mention has 

 been made- in previous pages of the insect scourges of the 

 hop grower, they may here be briefly summarized. Among 

 the insects injurious to the hop are the caterpillars of the 

 ghost moth (Hepialus humuli), which gnaw the roots of the 

 hop plant till the shoots are weakened, and the leaves droop 

 in bright sunshine, the aphides, or plant lice, known as the 

 green fly (Aphis humuli), the plant mite, or red spider (Aca- 

 rius telarius), and the wireworm. Curtis says the smaller 

 wireworms are very often the larvae of Elater Uneatus and 

 E. obscurus, and the larger ones of E. ruficandis. Hops in 

 Kent, Worcester, and Herefordshire are often reported to be 

 injured by the wireworm. The Eev. E. Sidney, in a lecture 

 on Parasitic Fungi, published in the * Journal of the Koyal 

 Agricultural Society,' vol. x., p. 394, states that hops are occa- 

 sionally damaged by an erysiphe, having the habits of that of 

 the pea, which seems to be in its early stage a peculiar mould. 



The vapour of heated sulphur is usually tried for the red 

 spider, and tobacco water is obnoxious to the aphides. 



