New Yorx AGRICULTURAL EXPERIMENT STATION. 311 
on the interior. The irritation produced by these operations gives 
rise to a thickening of the leaf which is known as a gall or blister. 
Within these galls eggs are deposited, and the young find subsist- 
ence, channeling in all directions, and develop to maturity. Through 
the tiny openings in the under surface of the gall the adults pass 
to and fro, and seek other spots to produce fresh galls in which to 
start new colonies. The production of young and the migration of 
adults is continuous through the growing season, and in favorable 
years the numbers of the mites are sufficient to completely infest 
the unfolding leaves of the new growth as they appear. Mature 
nites are present in the leaf tissues during the first week of May, 
and from then on through September eggs and larvae are present 
in the leaves. During the latter part of May and the first of June 
the mites in greatly increased numbers may be found in the pubes- 
cence of the young wood, upon the leaf stems and upon the unfold- 
ing leaves of the new growth. During October the mites largely 
abandon the leaves and swell the numbers already in hiding in the 
buds and in the pubescence of the bark of the new wood. Hiberna- 
tion occurs under the bud scales and apparently none of the mites 
pass the winter in the pubescence or in the crevices of the bark. 
ECONOMIC IMPORTANCE. 
The mite has largely attained its prominence as an orchard pest 
because of its destructive work on pear foliage. The literature 
upon this species is voluminous and it is almost entirely concerned 
with the economy of the mite in its relationship to pear growing. 
The references to the infestation of other plants are for the most 
part mere records of the host’s name and give no suggestion of the 
probable importance of the injuries committed by the mite. The 
work of the species in this capacity seems to be of little consequence, 
for important outbreaks would not have escaped the attention of 
economic workers. As a pear pest it is undoubtedly well known 
wherever this kind of fruit is grown. As such it is recognized in 
Europe, Russia, England, Canada, United States, Australia and 
Tasmania, and there are without doubt other countries where it is 
present. 
