HISTORY OF STAFFORDSHIRE. [39 



the approach of the board the flies hop, and are entangled in the 

 fresh paint, which must be renewed as often as necessary, or tar 

 may be used instead of paint. The following system is proposed 

 by the inventor : Take two boards, half an inch thick, from a deal 

 plank, connect them together by three or four pieces of cord, leav- 

 ing an interval between them of about a foot ; both the boards to be 

 painted, or tarred on the top ; some strings or fringes of netting 

 hanging loosely from the hinder edge of the first board will, by 

 playing on the ground, make many of the insects hop and alight on 

 the second : a strip of wood to be nailed under the fore-edge of 

 each board to keep it from warping or catching the ground, will 

 make them mount any clod or stone in their way. A piece of cord, 

 four or five feet long, is to be put through each fore corner of the 

 first board, with a cross stick at its fore end, to be drawn by a person 

 at each end. If the boards be twenty feet long, and laid crosswise, 

 they will thus sweep twenty feet in breadth ; and two persons in 

 going less than half a mile will sweep an acre, and in going five 

 miles will sweep more than ten acres : by following the hinder 

 board, you will have the pleasure of seeing the enemy entangled in 

 the paint or tar. The operation to be repeated daily, or twice a- 

 day if necessary, until the turnips get into the rough leaf, when 

 they will be secure from further danger. 



Mildew on Turnips, caused, as is generally supposed, by the 

 aphis brassier, an insect so extremely minute in its animalcule 

 state, that fifty or more may be found beneath one pair of seedling 

 leaves of a young turnip plant. In its fly state it has four wings, 

 two long and two short, body black, size of a grain of mustard seed, 

 is extremely prolific, and produces ten generations in one season, 

 each successive generation beginning to breed at ten or twelve 

 days old. First generation (oviparous), hatched by the sun ; the 

 succeeding ones, except the last (viviparous), and fifty on an ave- 

 rage produced at a time ; so that the production of a single fly in a 

 season is 50x50x50, to the tenth power, which amounts to countless 

 millions. Dr. Darwin believed this species to be so wonderful in 

 its increase, that, from their immense numbers, they may in pro- 

 cess of time destroy the vegetable world. The top-dressings before 

 mentioned are very probable means of checking the progress of 

 their increase. 



Turnip Tenthredo (tenthredo rustica), less frequent on turnips 

 than the former, common on willows, and when they increase beyond 

 the usual numbers, resort to turnip-fields. Great ravages were 



