THE INSECT WORLD. 



plish its mission, — the fertilization of the female. After this the 

 life histories differ greatly ; sometimes the female lives through 

 the winter in the partly-grown or adult condition ; sometimes she 

 lays eggs which fill up the entire space beneath the scale, the 

 insect itself shrivelling up until scarcely a trace remains. Some- 

 times living young are brought forth, and there may be one or 

 several broods. Hence it is necessary to study each species in 

 detail before we can say much on the subject of remedies. It is 

 obviously beyond the province of this book to describe all the 

 injurious species, and general statements only are possible. 



Fig. 86. 



Oyster-shell scale, Mytilaspis poniorum. — a, female scale, from beneath, filled with 

 eggs ; b, same, from above ; c, twig infested by female scales ; d, male scale and a twig 

 infested therewith. 



Perhaps the most common forms of this series are the ' * oyster- 

 shell" bark-lice, of which we have several species, deriving their 

 common name from the fact that the scales have a marked resem- 

 blance to the shells of some oysters. In the Northern United 

 States Mytilaspis pomorum is the common form, infesting apple 



