io8 THE TREE BOOK 



fall to fhe ground, in from three to five days, a 

 small army develops. 



Always the trees are more or less beset by the 

 ravages of scale insects and plant lice. These 

 pests lie close upon the bark of twigs and 

 branches and on the skin of leaf and fruit to 

 suck the juices. Among them, the San Jose 

 scale is the one most dreaded by orchard men. 

 This insect is very minute, being only one thirty- 

 second of an inch in length at maturity. Yet, 

 if unchecked, it will soon destroy an orchard, a 

 single female having been estimated to produce 

 a progeny of over one and a half billions in a 

 single season! The aphids, or plant lice, are 

 small sucking insects, most diflScult to combat. 

 They often attack the roots as well as the parts 

 above ground, and their multiplication is very 

 rapid. They live in clusters, and secrete over 

 themselves small patches of a cotton-like cover- 

 ing. 



The grape-vine bark louse is an aphid. It 

 lives under an odd brown, hemispherical scale, 

 with one end shut in by a cotton-like "awning." 

 This awning forms an ideal nursery for the 

 young aphids. 



If we keep our eyes open for them, we may 

 discover many odd and ingenious nurseries es-' 

 tablished in the trees by their cheeky little ene- 



