78 First Report on Economic Zoology. 
lime trees. There are a number of species of Oribata ; one, 0. globata, 
is often present in swarms on fruit trees, especially the plum. 
Instead of finding them injurious, they appear to be either beneficial 
or non-obnoxious. They have been seen feeding off the spores of the 
canker fungus and various green vegetal matters on fruit trees. But 
in one or two instances fruit-growers have noticed that they have 
done some harm to the leaves. They often swarm in the forks of 
the boughs and axils of the twigs and buds. The species sent by 
Mr. Birknell has been identified by Albert Michael as Oribata 
orbicularis , which also occurs on various fruit trees in Kent. 
This species has been dealt with in the Journal of the South- 
Eastern Agricultural College (No. 6, p. 11 (1897)). Albert Michael, the 
chief authority on Mites, agrees that these Oribatkke do no practical 
harm. Several fruit-growers have informed me that they cause the 
leaves of the plum to die off, however. It is possible this may have 
been due to other causes. All cases personally investigated have 
shown no damage to the trees, although thousands of these shiny mites 
were present. 
Treatment. 
Soft soap wash as suggested by a correspondent would be quite 
useless. The Oribatidse have very hard chitinous skins, and probably 
no wash that could be used in the summer would affect them. Late 
in the autumn caustic alkali wash might be tried and might prove 
beneficial. 
The method of preparing and using the alkali wash will be found 
in Leaflet 70 of the Board of Agriculture. 
The Pear-Leaf Blister Mite. 
( Eriophycs pyri, Sell.) 
Several enquiries were made concerning the Pear-Leaf Blister 
Mite during 1902. Information was sent that these little acari 
enter the leaf by the stomata and live in the soft internal tissues, 
where they soon commence to form a galled patch. They move from 
leaf to leaf, but spread very slowly. Often one tree in an orchard 
will be attacked for years before any neighbouring ones show signs of 
having contracted the disease. Frequently we see a single branch of 
a tree diseased year after year and yet the rest of the tree remains 
clean. In nearly all cases I have seen, the fruit becomes hard and 
gritty and is usually deformed. All we can do is to hand-pick the 
