5o8 



Mussel Scale. 



pest, one of the most injurious British scale insects, is also found 

 in North America, Australia, New Zealand, and South Africa, 

 having been imported on nursery stock. In this latter way it is 

 also largely distributed in this country. The necessity of 

 fumigating young . stock before planting is thus rendered 

 essential and should be done by all nurserymen before their 

 stock is sent out. A few scales may easily escape detection and 

 so set up a large colony, to the detriment and even death of the 

 tree. There is no district in England where this pest does not 

 occur in greater or less abundance. Old trees and neglected 

 orchards chiefly encourage it, but young stock suffer far more 

 than old. 



This scale insect is frequently taken for growths on the bark ; 

 but the scale is the product of a minute insect belonging to the 

 Coccidce. The male and female scales differ in appearance and 

 size ; the former being seldom observed. 



The insect damages the trees by sucking out the sap with a 

 long, flexible mouth, which it inserts into the plant tissues. 

 It occurs not only on the trunk and boughs, but also on 

 the leaf and fruit. Foreign apples are frequently imported 

 covered with this and other scale pests. The scale, as in all 

 Coccidce, is a product formed by the insect which lives beneath 

 it, partly by excretions from its body, partly by the cast skins 

 of the insect, the so-called exuviae. 



Life History. 



The female scale (Fig. a, b) is about one-eighth of an inch long. 

 It is rounded at the end, but tapers to a point at the head ; it 

 may be straight or curved, and even much contorted. In colour 

 it varies from deep brown to almost grey. The male scale is 

 much smaller than the female and of the form shown in Fig. c. 



The eggs are laid by the sedentary female under the scale. 

 They resemble to the naked eye small whitish dust. As 

 many as eighty may be counted under a single scale, but the 

 number varies considerably. The eggs give rise in the early 

 summer to very small, active six-legged larvae, which crawl 

 from beneath the scales and may be distributed from tree to 

 tree by the wind, by birds, and by predatory insects, such as 

 lady-birds. They are about one-hundredth of an inch long. 



