No. 4.] THREE SHADE-TREE INSECTS. 



245 



July. The young lice migrate to the leaves and after feed- 

 ing on the plant juices throughout the summer, return to the 

 branches with the approach of cold weather and prepare to 

 hibernate. According to Prof. L. O. Howard, the males 

 appear late in May and the females give birth to the young 

 in from three to four weeks from the time of pairing. 



Food Plants and Damage. 

 The bark louse was probably brought to this country upon 

 European elms. It occurs commonly on the Camperdown 

 and Scotch elms and also inflicts serious injury to the Amer- 

 ican elm, the slippery elm and the cork elm. The greatest 



Fig. 5. The Elm Bark Louse, a, adult female from below; b, adult female from Bide; c, 

 adult female from above — all greatly enlarged; d, empty wax cushion; e, females in 

 natural position — enlarged ; /, shrivelled females, natural size. (From "Insect Life.") 



damage to elms from this insect occurs on young trees re- 

 cently taken from the nursery. As factors in the dissemi- 

 nation of this insect, nurseries have played a most important 

 part. In fact, the first complaint of damage from the elm 

 bark louse was reported from a large nursery in New York. 



