INDIRECT INJURIES CAUSED BY INSECTS. 187 



lion was made throughout the island for the relief of the 

 poor, whose principal food it forms. 



The chief dependence of our farmers for the suste- 

 nance of their cattle in the winter is another most useful 

 root, the turnip. And they have often to lament the di- 

 stress occasioned by a failure in this crop, of which these 

 minor animals are the cause. On its first coming up, as 

 soon as the cotyledon leaves are unfolded, a whole host 

 of little jumping beetles, composed chiefly ofHaltica Ne- 

 morum, called by farmers the^ a and blackjack, attack 

 and devour them ; so that on account of their ravages 

 the land is often obliged to be resown, and frequently 

 with no better success. It has been calculated by an 

 eminent agriculturist, that from this cause alone the loss 

 sustained in the turnip crops in Devonshire in 1786 was 

 not less than 100,000/. b Almost as much damage is 

 sometimes occasioned by a little weevil (Ceutorliynchus 

 contractus) which in the same manner pierces a hole in 

 the cuticle. When the plant is more advanced, and out 

 of danger from these pygmy foes, the black larva of a 

 saw-fly takes their place, and occasionally does no little 

 mischief, whole districts being sometimes nearly stripped 

 by them; so that in 1783 many thousand acres were on 

 this account ploughed up c . The caterpillar of the cab- 

 bage-butterfly (Pontia Brassicce) is also sometimes found 

 upon the turnip in great numbers ; and Sir Joseph Banks 

 informs me that forty or fifty of the insects before men- 



a The farmers would do well to change the name of this insect 

 from turnip-fly to turnip-flea, since from its diminutive size and acti- 

 vity in leaping the latter name is much the most proper. The term, 

 the fly, might with propriety be restricted to the Hop-aphis. 



b Young's Annals of Agriculture, vii. 102. 



c Marshall in Philos. Trans. Ixxiii. 1783. 



