240 ANNUAL REPORT OF THE Oft. Doc. 



Hedge plants are often badly infested. Japanese quince is one of 

 the worst, and Osage orange conies very closely after. 



In fact it may be said that there is scarcely a deciduous shrub or 

 tree on which the insect may not maintain itself, though it may not 

 cause actual injury. On shade and forest trees, it does not seem to 

 cause much trouble. I have seen it abundantly on small European 

 elms, and, to a lesser extent, on the American varieties; but never on 

 older trees to a troublesome extent. So I have found it rarely on 

 maple and poplar and very abundantly on willow. The latter is 

 sometimes injured and I have seen the Kilmarnock variety killed by 

 the scale. 



Of the nut trees, hickory and walnut may be infested and the lat- 

 ter may be injured. Chestnut may become infested, but the insect 

 does not thrive on it and the trees do not suffer. 



Conifers are entirQly exempt from attack so far as I have observed, 

 and privet is practically so; hence we are not left entirely without 

 hedge or ornamental plants. 



Herbaceous plants, or such as kill down to the root during the 

 winter, do not serve as host plants for the pernicious scales, because 

 they cannot hibernate on it. 



The insect is absolutely dependent upon the tissue upon which it 

 is fixed, and if the latter dies, the insect dies also. If a scaly leaf 

 drops to the ground, every scale dies as soon as the leaf is dry. The 

 same is true of a twig or branch when cut from the tree; hence, if 

 trimming is done during the winter in a scaly orchard, the cut wood 

 may be safely left on the ground. The insects canot leave it, and 

 long before the commencement of the breeding season all sap will be 

 out; so, the insects having had nothing to feed upon, will be dead. 



THE INJURY AND HOW IT IS CAUSED. 



When a scale-insect first fixes itself upon a succulent twig or 

 fruit and begins to pump out the plant juices, no immediate change 

 is observable. But after a week or two a faint reddish tinge becomes 

 evident around the scale and in the bast from which it feeds. As the 

 insect grows, a depression is apt to be found on the bark where it is 

 lodged and the red tint becomes more obvious. On the fruit it is 

 often so marked, that an infested tree in bearing, is most readily de- 

 tected by the prominent spots on the fruit. The discoloration is 



