MONTANA EXPERIMENT STATION. 



167 



Fig. 15. The Greedy Scale Insect: a, female scale from above; b, same 

 from below: c, mass of scales as appearing on bark; d, male scale; e, male 

 scales on twig; i. female scales on twig; e and f, natural size; c, considerably 

 enlarged; a, b, d, greatly enlarged. (Howard, Yearbook, U. S. Dept. of 

 Agr„ 1894.) 



THE OYSTER-SHELL BARK LOUSE. 



The oyster-shell bark louse is the best known of any of the or- 

 chard scales. It probobly came originally from Europe but it is 

 now known throtighout the world. Like the other scale insects 

 here discussed it is particularly adapted to distribution on nursery 

 stock. 



This insect attacks a variety of food plants including apple, pear, 

 plum, quince, hawthorn, raspberrq, currant, linden, willow, cotton- 

 wood, poplar, wild cherry, rose, lilac , and white birch. Many of 

 these it attacks so severly as to threaten their lives. 



The scales of the two sexes are quite different in size and appear- 

 ance. The female scale is elongated (see "a" of the figure) rounded 

 >jii the upper surface, flat beneath, and brownish in color. The 

 male scale is much smaller but of the same color. 



If one of the female scales be turned over during the winter 

 there may be seen numerous very minute white eggs closely packed 



