MISCELLANEOUS CROPS. 151 



about the eighth day after birth, so that the issue from a 

 single individual easily runs up, in the course of the sum- 

 mer, to trillions. . . . Therefore a single stem-mother 

 may, under favouring circumstances, blight hundreds of 

 acres in the course of two or three months." 



Prevention. — (1) Trees belonging to the genus Prunus 

 should be thoroughly washed with lime in both the 

 autumn and spring. (2) The natural enemies of the 

 Aphides are the larvse of the Coccinellidce (the "lady- 

 bird " beetles). 



Cure. — The most effectual remedy iised in this country is 

 a decoction of soft-soap and tobacco (20 lbs. of soft soap to 

 100 gallons of water, and then j lb. of tobacco added). Mr. 

 Whitehead, F.L.S., says that " the cost of washing varies 

 from thirty to thirty-five shillings per acre each time it is 

 done. Great care must be taken to wash every leaf under- 

 neath, and the process generally must be repeated twice 

 or even thrice." " Washing is done by means of a large 

 garden-engine, fitted with a pump, and a long length of 

 gutta-percha hose on each side, having a single jet, or 

 rose, or spray syringe, which can be directed under the 

 leaves and round the bines, thoroughly cleaning the 

 plants " (Ormerod). But undoubtedly the best machine 

 for this and similar purposes is the Pneumatic Distributor 

 or Strawsonizer invented by Mr. Gl. F. Strawson, of New- 

 bury. In this machine both liquid and solid insecticides 

 are distributed by means of a blast of air '' produced by 

 a fan actuated by the travelling wheels of the machine, 

 and worked up to a velocity of 3,600 revolutions per 

 minute." 



The Hop Flea {Haltica concinna) belongs to the 

 same genus as, and is somewhat like, the " turnip fly." 

 The hop flea, or beetle, causes considerable damage, in the 



