Insects Injurious to the Apple. 



167 



reveal these little pests. Young trees are often infested too, but 

 one is not so sure of finding them on young, well cared for trees, 

 as on old and neglected ones. 



The Mussel Scale is so called because the scale roughly resembles 

 in shape a miniature mussel shell. It is also called the Oyster-shell 

 Bark Louse, because it also bears some similarity to the American 

 Blue-point Oyster. In size and exact shape there is much variation. 



FIG. 139. THE MUSSEL SCALE (Lepidosaphes ulmi). 



1, female scale (dorsal view) (x 15); 2, ventral view with ova (X 15); 3, mature female beneath 

 scale (X 20) ; 4, larva (X 50) ; 5, male (X 35) ; 6, male scale (X 15). 



(After Xeu-stead.) 



Most insects vary in size, the quantity and quality of food regulating 

 the growth. Most mussel scales will be found to vary between and 

 inch in length. In form the hard scale is swollen and rounded at 

 one end, more or less bluntly pointed at the other, the whole scale 

 somewhat flattened in form, and very closely applied to the bark. 



