32 



under the scale on to the bark of the tree, where they wander 

 about for three or four days, and may during this period be 



c. 



Q. 



FIG. 2. 



a. Female Mussel Scale, dorsal view; 6. The same, ventral view: 

 c. Male scale. 



carried to other trees by means of the wind or by clinging to 

 birds and insects. When one of these " lice " (larvae) reaches 

 a suitable spot, it drives its " trunk " (or proboscis) into the 

 bark and begins to feed by sucking up the sap just like a 

 Green Fly or a Capsid Bug. Unlike either of the latter pests, 

 however, it soon loses all ' power of movement and remains 

 fixed to the bark in which its trunk is buried. As it grows 

 it forms the scale under which it lives, building up the scale 

 in such a way that the insect itself is always completely covered 

 (Fig. 2). 



In the case of the Mussel Scale, the insects are practically 

 all females, and when they become adult towards the end of 

 summer they lay eggs (as a rule without the intervention of 

 a male) under the scale, continuing until there may be as many 

 as 80 eggs under one scale. The female then dies and the 

 eggs remain in safety under the scale during the winter. 

 Mussel Scale insects of the male sex do occur, but they are 

 very rare on fruit trees. When young, the males, like the 

 females, live under scales, but the male scales are somewhat 

 different, being straighter and not so large (Fig. 2c). Under 

 the scale the young male passes through a pupal (chrysalis) 

 stage, and on becoming adult emerges as a minute fly-like 

 insect with two wings. The males pair with the females and 

 soon die, having no mouth parts for feeding. 



Plants attacked and Nature of Injury. Mussel Scales are 

 injurious to apples, and less frequently to pears and currants 

 (both black and red). The insects also attack sallow, haw- 

 thorn, broom and other plants.. Trees gro'vi'ig against walls 



