PEAR LEAF-BLISTER MITES. 



127 



Pear Leaf-blister Mites. Phytoptus pyri, Nalepa. 



Phytoptus pyei. — Female, nat. length circa 0-2 mm. ; left leg of the first pair 

 of P. tristriatus, and (smaller figure) of P. tristriatus var. carinea, magnified 

 550 times — all after Dr. Nalepa. Infested Pear leaf. 



The Pear-leaf disease, known as " blister," which is caused 

 by a minute cylindrical four-legged mite (or acarus), figured 

 greatly magnified above, does great harm to Pear leafage in 

 some places in this country, and likewise on the Continent of 

 Europe, and in the United States and Canada. 



The disease shows itself in the form of blister-like spots 

 somewhat raised on each side of the leaf, and in the middle of 

 each little blister beneath the leaf is a little hole, which gives 

 access to the central cavity, and also gives passage out at 

 pleasure to the mites. The spots or blisters may be found on 

 the Pear leaves whilst they are still quite young ; but later on, 

 when the leaves are expanded, is the period at which they are 

 most noticed. They may be red or green, or red on one side 



