HOMOPTERA 459 



it, notwithstanding its limited distribution, I stated: "From what I 

 have seen of it, I think that it is the most pernicious scale-insect 

 known in this country." Since that time it has become widely dis- 

 tributed. Slingerland and Crosby write of it as follows: "The San 

 Jose scale has attained greater notoriety, has been the cause of more 

 legislation, both foreign and interstate, and has demonstrated its 

 capabilities of doing more injury to the fruit interests of the United 

 States and Canada than any other insect." 



This species infests various fruit-trees and ornamental shrubs ; it 

 infests the bark, leaves, and fruit of its hosts, and usually causes 

 reddish discolorations of the bark and of the skin of the fruit. 



This species can be distinguished from the other scale-insects 

 that are important pests of our fruit-trees by the form of the scales. 

 The scale of the female is circular and flat, with the exuviae central, 

 or nearly so. The scale is gray, excepting the central part, that which 

 covers the exuviee, which varies from a pale yellow to a reddish yellow. 

 It measures 2 mm. in diameter. The scale of the male is black, and is 

 somewhat elongate when fully formed. The exuvis is covered with 

 secretion; its position is marked by a nipple-like prominence which 

 is between the center and the anterior margin of the scale. 



Control of scale-insects. — The extensive damage that has been done 

 by scale-insects to fruit-trees and to cultivated shrubs has led to many 

 experiments in the destruction of these insects. The results have been 

 quite satisfactory ; with proper care, it is now possible to keep in 

 check the ravages of these pests. Detailed accoimts of the methods 

 to be employed are given in many easily available publications, and 

 especially in bulletins of experiment stations. 



In the case of deciduous trees and shrubs, the best time to destroy 

 scale-insects infesting them is during the winter, when the trees are 

 bare and in a dormant state. At this time the entire tree can be 

 reached with sprays, without the interference of leaves; and, too, 

 certain sprays can be safely used that are liable to injure the trees 

 during the growing season. This is especially true of the lime-sulphur 

 mixture, which is very widely used for the destruction of scale-insects, 

 and is very effective. Among the other insecticides used for this 

 purpose are kerosene emulsion and dilute miscible oils. For summer 

 spraying, whale-oil soap, one pound dissolved in four or five gallons 

 of water, can be safely used. 



In the case of trees that are constantly clothed with foliage, the 

 effective use of sprays is more difficult. In the orange-growing sections 

 of California the trees are fumigated with hydrocyanic acid gas, th^ 

 tree to be treated being first covered with a large tent. 



