MONTANA EXPERIMENT STATION. 209 



THE 0Y5TER=SHELL BARK=LOUSE. 



Lepidosaphes ulmi (Linn.) 



This widely known injurious species is the only scale insect of im- 

 portance to the fruitgrower that, so far as is known to the writer, has 

 been recognized in Montana. It appears to be generally distributed 

 in the state, particularly west of the main divide, where in some 

 cases it has proved to be a serious enemy to apple trees. One orchard 

 of 800 trees in the Bitter Root valley is so badly infested as to show 

 its sickly condition at a considerable distance. Nearly every smaller 

 limb and twig on the greater number of the trees is thickly incrusted. 



There can be little doubt that this scale insect, which was known 

 in Europe upward of a century ago, was imported into America on 

 nursery stock by the early settlers and later transferred to Mon- 

 tana from other parts of the United States in the same way. 



FOOD PLANTS. 



The oyster-shell bark-louse has been recorded on a large number 

 of food plants, the total number for America being about forty. The 

 list included, beside apple and pear, various other fruits and prac- 

 tically all the more important shade trees of northern United States. 



Dr. Howard has suggested that eventually two species instead of 

 one may be found in the series in the list of food plants. 



LIFE HISTORY AND HABITS. 



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

 be found to contain a mass of very minute yellowish-white 

 eggs, and in the pointed anterior end of the scale, the shrivelled 

 body of the female. Dr. Howard has found the eggs under each 

 scale to vary in number from 42 to 86. 



In the New England states these eggs hatch about the first of 

 June, varying in different years according to the forwardness of the 

 season.. We have had but little opportunity to make observation on 

 this point in Montana, and have but one record. On June 5, 1903, 

 none of the eggs had hatched at Lo Lo. The young (Fig 3, c.) are 

 able to walk immediately after hatching, and working their way out 



