125 
Figs. 24 and 25.—Leaves of the pear tree, showing two stages of the galls pro- 
duced by Phytoptus pyri (after Sorauer). H. Garman, del. 
The pear-leaf blister (Figs. 00 and 00,) is the result of a disease 
which is widely known, but not commonly understood to be due to 
the ravages of mites. Such: is, however, the fact, as is now well 
known to foreign horticulturists. Recently, Prof. T. J. Burrill has 
discovered mites in blistered pear leaves in this State, and tells us 
that they are identical with the European Phytoptus pyri*, a species 
which he thinks has been introduced with imported pear trees. In 
an account of this malady, which he has kindly furnished me (see 
Phytoptus pyri, Scheuten, at the end of this paper), he says, regard- 
ing the effect of this mite’s work upon the pear trees : 
“Trees are not killed outright, but much injury is done by this 
work upon the leaves; sometimes, also, the much more deadly 
‘blight’ shoots from the minute wounds made by the mites. A tree 
* Since the above was written, I chanced upon a reference to the work of this mite on 
our pear trees, in the report for 1872 of the U. 8. Entomologist. 
