178 EXPERIMENTAL FARMS. 
63 VICTORIA, A. 1900 
Series), the use of hydrocyanic acid gas for greenhouse fumigation is recommended, as of 
particular value to violet growers. Indeed this line of application of the gas is said to 
have been specially devised for violet houses by Messrs. Woods and Dorsett, the authors 
of the bulletin, who are officers of the Division of Vegetable Physiology and Pathology, 
and the latter is a practical violet grower. Careful and exact directions as to the proper 
way of using the gas, together with the necessary precautions which must be taken to 
avoid danger to the plants or to the operator, are given. Different plants are liable to 
injury in a varying degree, so that it becomes necessary to know the strength of the gas 
which may be used with each class of plants. Many experiments have been tried with 
this end in view, and directions are given in the bulletin cited for some of the leading 
greenhouse plants, e.g. : 
‘Double English Violets.—“ Marie Louise,” “Lady Campbell,” and others. For plant- 
lice and general fumigation, fifteen-hundredths of a gram of 98 per cent cyanide of 
potassium for each cubic foot of space is required. The exposure, if made according to 
directions, will not hurt the plants in any stage of growth. The gas has been used on 
a large scale in fumigating violets for the past three years with the greatest success, only 
a few treatments during the season being required. Leaf-eating larve, slugs, millipedes, 
cutworms, &c., when exposed, are killed as well as plant-lice. Red Spiders, however, are 
not entirely eradicated by the treatment. The foliage of single violets like California 
and Princess of Wales are sometimes slightly injured by the stronger dose of gas. A 
weaker dose (one-tenth of a gram cyanide of potassium per cubic foot) should be used 
when they are to be treated.’ 
THE CLOVER MITE 
(Bryobia pratensis, Garman). 
Attack.—Reddish brown mites ;/, of an inch in length, oval in shape and with 
remarkably long front legs, causing the leaves of fruit and other trees, as well'as of 
clover, to turn yellow. 
This species of mite belongs to the same family of vegetable feeding mites, the 
Tetranychide, as the ordinary so-called ‘Red Spider,’ often found on house plants 
and in conservatories, and which also attacks orchard trees, rose and currant bushes, 
sweet peas, and other low plants, causing the leaves to assume a sickly appearance and 
to dry up. The eggs of the Clover Mite frequently come in from inquiring correspond- 
ents. They are ruby redin colour, broadly rounded above and comparatively large, about 
zioth of aninchin diameter. They are usually deposited in large flat mat-like clusters 
in and around crotches of the branches of orchard trees, particularly of plum trees, and 
often in sufficient numbers to give a distinct red colour to the bark. Specimens of eggs 
were received first from British Columbia, and since then have come from many parts of 
Ontario, and as far east as Gaspé in the extreme east of the Province of Quebec. 
Though spread over such a large territority in Canada, the Clover Mite does not 
seem to have attracted attention by its injuries anywhere except in British Columbia, 
until last summer, when the following letter was received : 
‘Queenston (Lincoln Co.), Ont., July 17.—With this I send you some twigs of 
some Niagara Plum trees. They are much paler green than others and are evidently 
affected by some insect, possibly the Red Spider. Did you ever know this insect to 
work on plum trees in this manner? The entire foliage of large trees seems affected. 
What had I better do to check it? Is it dangerous?’—C. E. Fisuer. 
In Canada the Clover Mite passes the winter in the egg state, but in many parts of 
the United States it has been complained of from time to time in the last ten years as 
an unwelcome invader of dwelling houses in the mature state, during autumn and winter. 
The small size of the Clover Mite enables it to go through ordinary wire screens with 
ease to the serious disquietude of the house-keeper. 
The large number of inquiries about this mite, both on account of its invasion of 
houses in autumn and of its injuries on trees and other plants, made it necessary for the 
United States Entomologist to publish a special circular on the subject (Circular No. 
19, Second Series). 
