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XIX. — Observations on the Natural History and Economy of the 

 different Insects affecting the Turnip Crop. By John 

 Curtis, F.L.S., &c. Paper I. 



Unless we collect facts on good authority, and conduct ex- 

 periments with care and perseverance, our labour will be lost in 

 studying the economy of the insect tribes ; for in the investiga- 

 tion of such living atoms, as they often are, the slightest error 

 may lead us far from the truth. It is not to be expected that 

 a taste for such studies will be universal, though all who can ap- 

 preciate the value of a good harvest will take, it may be fairly 

 presumed, an interest in our researches. Such a taste, however, 

 where it does exist, is easily improved ; and it is a truth 

 admitted by all who have indulged in such pursuits, that they 

 never repented of the time that had been given up to these laud- 

 able objects ; and independently of the amusement to be derived 

 from the investigation of nature, any benefits conferred on man by 

 such knowledge ought ever to be a source of real satisfaction, and 

 of honest pride, to every cultivator of natural science, however 

 trifling his contributions may be to the general stock of in- 

 formation. 



Unimportant as insects may appear to the casual observer, 

 they often prove awful visitations when employed by the Creator 

 as his armies to fulfil his ends. No one suffers more from these 

 hosts than the agriculturist ; it is therefore impossible that he can 

 remain an indifferent spectator whilst it may be in his own power 

 to palliate, if not to avert, the evil. I therefore hope that these 

 memoirs, by calling the attention of the farmer to so important a 

 subject, may lead him to useful and profitable results ; and should 

 he derive as much advantage from their perusal as I anticipate of 

 pleasure in their detail, it will prove to me a source of unfeigned 

 gratification. 



I am aware that one of the greatest difficulties the farmer has 

 to contend with is that invariable law of nature which compels 

 him to change his crops, from the exhaustion of certain elementary 

 parts of the soil, which are absorbed or neutralised by the vege- 

 table that is produced ; and with all his art in selecting manure 

 and resting the land, it will become tired at last, and by degrees 

 refuse to produce certain crops nearly altogether : it is even 

 asserted of the turnip, that it certainly does not grow so vigorously 

 nor so readily as it did several years ago. It is natural to suppose 

 that as this period approaches the crops will become, from feeble- 

 ness, more susceptible of disease ; and as insects are intimately 

 connected with this subject, contributing in no small degree to 

 the dissolution of vegetables, and the failure of our crops being 

 frequently very justly attributed to them, this is a matter well 



