186 INDIRECT INJURIES CAUSED BY INSECTS. 



soon as the cotyledon leaves are unfolded, a whole host 

 of little jumping beetles, composed chiefly of Haltica Ne- 

 morum, called by farmers the Jh/ 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 1 00,000/. a Almost as much damage is 

 sometimes occasioned by a little weevil [Curculio con- 

 tractus, E. B.) 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 [Tenthredo, L.) takes their place, and occa- 

 sionally 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 b . — 

 The caterpillar of the cabbage-butterfly (Papilio Bras- 

 sicce, L.) is also sometimes found upon the turnip in 

 great numbers ; and Sir Joseph Banks informs me that 

 forty or fifty of the insects before mentioned c , called by 

 Mr. Walford the wire-worm, have been discovered in 

 October just below the leaves in a single bulb of this 

 plant. — The small knob or tubercle often observable on 

 these roots is inhabited by a grub, which, from its re- 

 semblance to one found in similar knobs on the roots of 

 Sinapis arvensis, from which I have bred Curculio con- 

 tractus, E. B., and Rynch&nus assimilis, F., is probably 

 one of the same or an allied species d . This, however, 



a Young's Annah of Agriculture, vii. 102. 



b Marshall in Pfiilos. Trans. Ixxiii. 1783. 



r Sec above, p. 166-167. 



d Swamm. ii. 81. col, b.— Gyllenhal in describing the last-named 



