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4 LETTERS ON ENTOMOLOGY. 
is evidently established by long experience, as 
the peasants anxiously watch all the rest of the 
year, whether the wild figs will be likely to 
produce flies in time, and the number of them 
determines the harvest of fruit. Indeed so ne- 
cessary are these insects, that if they fail, the 
people have but one resource, which is, to spread 
over the trees a common plant called the asco- 
lombros, the fruit of which contains flies fit for 
the purpose. 
The ancients used many kinds of insects as 
medicine, but I shall only mention the can- 
tharides or blister-fly, which is so useful in many 
disorders. 
Now, my dear Harriet, let us change the scene, 
and consider the variety of mischief they may 
do us, if we do not know how to guard against 
them, which we shall not find easy, unless we 
previously know something of their habits and 
nature. A great number ravage not only our 
fields and gardens, but our houses, our furniture, 
and our garments ; they do not even spare our 
persons ; yet we are not to be alarmed, or fancy 
ourselves sadly aggrieved, if they make use of 
the weapons given them for their just defence ; 
for they have certainly as much right to live as 
ourselves, and those who wantonly destroy them 
