INJURING THE BRANCHES. 



151 



the Spotted Willow Aphis described above, except 

 that it prefers the trunk and larger limbs to the 

 twigs. The sexed individuals appear in autumn, 

 and the eggs are probably laid upon the bark. The 

 species is characterized by a large tooth-like tubercle 

 on the middle of the back of the abdomen (Fig. 77). 

 Remedies. — A strong kerosene emulsion sprayed 

 upon the bark will destroy these creatures. 



The White Pine Aphis. 



Lachnus strobi. 



This insect is a widely distributed species, and on 

 account of its egg-laying habits it is liable to be in- 

 troduced everywhere with pine trees from nurseries. 

 It frequently becomes so numerous as to do serious 

 injury to White Pines in ornamental grounds. 



Like most plant-lice, this species reproduces vivi- 

 parously, or by giving birth to living young, during 

 the summer, but on the ap- 

 proach of cold weather the 

 sexual individuals are pro- 

 duced. During October these 

 are usually the only forms 

 present, the oviparous f e - 

 males being congregated in 

 great numbers upon the bark 

 of the smaller branches, with 

 their heads nearly always 

 directed towards the trunk 

 of the tree. When disturbed 



, -i , • i. Fig. 78. White Pine Aphis : 



they move about rapidly, oviparous female. Magnified. 



