The Scale Insects 



Life History of the Oyster-Shell Bark-Louse 

 of the Apple. 



(Mytilaspis pomorum Bouche" .,) 



This insect is probably the commonest and most widespread, 

 and consequently the best-known, of any of the orchard scales. 

 It is found all over the world. It was probably an European 

 insect originally at all events, it was known in Europe during 

 the last century and was probably imported into this country 

 on nursery stock by the early settlers. It is found in the United 

 States practically wherever apples and pears are grown, more 

 abundantly at the north than at the south, and has often received 

 treatment at the hands of writers on injurious insects. It was 



P'ig. 150. Mytilaspis pomorum. (Author's illustration.) 



certainly known in this country as early as 1794, and it unques- 

 tionably followed apple culture as it progressed to the west. It 

 was known in the districts bordering along Lake Michigan in 

 1840, and in 1868 it invaded Iowa and northern Missouri. To- 



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