INDIRECT INJURIES CAUSED BY INSECTS. 



149 



rise and fall of his wealth, as well as of a very important branch 

 of the revenue, the difference in the amount of the duty on 

 hops being often as much as 200,000/. per annum, more or 

 less, in proportion as the fly prevails or the contrary.^ 



If the beer-drinker be thus interested in the history of 

 these animals, equally so is the drinker of tea. Indeed mgav 

 is an article so universally useful and agreeable, that what 

 concerns the cane that produces it seems to concern every 

 one. This also affords a tempting food to insects. The 

 caterpillar of a white moth, called the horer, for destroying 

 which a gold medal has been long offered by the Society of 

 Arts, is, in this respect, a great nuisance, boring into the 

 centre of the stem, and often destroying a great proportion of 

 the crop. This insect (for his essay on which he received the 

 offered medal) has been described by the Rev. L. Guilding, 

 in the Transactions of the Society of Arts (xlvi. 143.), under 

 the name of Diatrcea Sacchari, which, however, Mr. West- 

 wood conceives is identical with Phalcena saccharalis Fab.^ 

 An ant also (^Formica analis) makes a lodgment in the in- 

 terior of the sugar-cane in Gruinea, and destroys it. — Another 

 species of the latter genus does not devour it, and is therefore 

 improperly called Formica saccharivora by Linne ; but, by 

 making its nest for shelter under the roots so injures the 



1 It would not be difficult to show that nearly the whole of this large sum, 

 and their own still greater losses, are thrown away by the hop planters from their 

 ignorance of entomology. Led by their old prejudices of the fly being produced 

 by cold Avinds, &c., they do nothing towards its destruction, though if aware of 

 the way in which it is generated (as lately explained), and that by killing each 

 female as it appears early in the spring, they would prevent the birth not of 

 thousands but of millions of aphides, were they to take measures for thus lessening 

 the number of their destructive enemy, they might in great measure secure 

 themselves from its attacks. The aphides being so soft are killed with the 

 slightest pressure ; so that it is merely necessary to rub an infested leaf between 

 the thumb and fingers, with a force quite insufficient to injure its texture, to 

 destroy every aphis upon it ; and, from experiments which I myself made in the 

 hop grounds of Worcestershire when at Malvern in 1838, I am persuaded that 

 every leaf of each hop plant might be thus cleared of the female aphides, first 

 attacking it in spring, by women or children mounted on step ladders for this 

 purpose, in ten minutes or less ; so that six plants being cleared per hour, sixty 

 might be cleared per day at an expense of a shilling for labour, and the first cost 

 of a few step ladders ; and by repeating the operation every week or fortnight, 

 there can be no doubt a hop plantation might be effectually preserved from the 

 fly ; as it might earlier in the spring from the /Zm (Haltica conc/rma), by shaking 

 them into a kind of wide and deep sieve (divided into two halves with a circular 

 space for the hop poles and hop stems) with a linen bottom and bag for pre- 

 venting them from jumping out again. 



2 Westwood, Modern Classif. of Ins. ii. 411. 



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