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XXXIIL — Observations on the Natural History and Economy 

 of the Turnifp Saw-Fly, and its Black Caterpillar, called the 

 Black Palmer, Black Canker, Black Jack, Black Slug, and 

 Nigger, or Negro. By John Curtis, F.L.S., Corresponding 

 Member of the Imperial and Royal Georgofili Society of 

 Florence, &c. 



Paper II. 



In studying tlie economy of insects, the striking irregularity in 

 their appearance is not one of the least curious and remarkable 

 facts that presents itself. We know from observation that what 

 has up to a certain period been an unnoticed or unknown species 

 of insect suddenly becomes abundant, and then disappears as un- 

 expectedly.'^ This will render it necessary to give the history 

 and details of all such as have at any period proved injurious to 

 the crops of Great Britain. It is deeply to be regretted that so 

 ]ittle notice has been taken of these events in standard works ; even 

 the few data which we obtain from such sources are so vague, that 

 it is frequently impossible to identify the insects alluded to ;j' and 

 yet such data are probably as essential to the understanding of the 

 eccentric succession of these phenomena, as astronomical observa- 

 tions are to explain the beautiful revolutions of the planetary 

 system. 



The unaccountable presence of the turnip saw-fly, and espe- 

 cially of its black caterpillar, producing marvellous conjectures 

 in the country, first led me to entertain a hope that the knowledge 

 and services of men of science might do much towards smoothing 

 the way to a correct knowledge of the natural history of insects 

 injurious to the farmer. It is to be hoped that the veil of super- 

 stition has long since departed with our ancestors ; but it is still 

 necessary to dissipate the clouds of error which obscure the 

 beauty of truth : this is the pleasing province of the naturalist, 

 especially of the entomologist ; and the natural history of the black 

 caterpillar being perfectly understood, its progress can be traced 

 from the egg to the fly so circumstantially, that the most scep- 

 tical need no longer remain in doubt respecting its economy. It 

 may be admitted that the sudden and unexpected appearance of 



* Innumerable mstances might be adduced, but one will be sufficient — 

 -Allantus flavipes, an insect of the same natural family as the subject of this 

 memoir, which did not exist, I believe, in a single English cabinet pre- 

 vious to 1838, when all at once it became abundant in Battersen-fields, and 

 the following year at Hampstead, feeding upon the common and white mus- 

 tards, and it is now quite lost sight of again. — Curtis's Brit. Ent., pi. and 

 fol. 764. 



f In various accounts of the wireworm, totally different animals have been 

 confounded under that appellation. 



