144 HOW TO LIVE IN THE COUNTRY 



Bear in mind always that the best protection for a 

 tree against insect attack is to keep it in good grow- 

 ing health. This is particularly true of the aphidae 

 or lice, that they put in their appearance largely as 

 scavengers, to clean up sickly foliage. A thrifty 

 houseplant stands a good chance of resisting their 

 attack and a well-kept and well-groomed apple tree 

 suffers far less from them than one in which the juices 

 are slow and the vitality low. Insignificant as the 

 aphidae are, their enormous numbers, the result of 

 most astounding rapidity of multiplication, make 

 them one of our most serious rivals. The hop louse 

 appears on our plum trees and buckthorn hedges in 

 spring, covering them with hordes of sucking and 

 killing beggars, and in midsummer sends off a gener- 

 ation with wings to destroy the hop yards. 



Professor Riley, United States entomologist, made 

 as pretty a study as science ever achieved in working 

 up this special pest. It is miraculous, the speed with 

 which these lice will cover the orchards of a whole 

 State, or of half a dozen States, and the worst of it 

 is that Nature seems to go over to their side and 

 help them out. The leaves curl up and make it 

 nearly impossible to hit them with a spray. More 

 than that, if you kill ten millions in the morning, be- 

 fore night there will be twenty millions more 

 hatched out and every one at work sucking the life 

 from the foliage. Professor Forbes estimates that 

 a single mother in a single season will produce nine 

 and a half quadrillions of young. It is hardly worth 



