MITES 547 



Bisulphide of carbon fumes are very poisonous, and should 

 not be breathed, and no naked light (the operator, for example, 

 should not be smoking) must be brought near them. 



Red spider. Several mites are included under the general 

 term 'red spider,' and judging from the literature on the 

 subject, opinion is divided as to the number of species 

 present in this country, and under what names they should 

 be known. This, however, in the present instance is not of 

 primary importance. The form so injurious to plants under 

 glass is called Tetranychus telarius, which spins a delicate web 

 on the under surface of leaves, etc. Leaves that are attacked 

 soon present a mottled yellowish appearance, and finally fall. 

 A dry, warm atmosphere favours the extension of the mite. 

 Syringing with a solution of potassium sulphide holds the 

 mites in check, if begun sufficiently early, but if the webs 

 are allowed to be fully formed, spraying is of little avail. 

 Under such circumstances the fumes of sulphur should be 

 resorted to as the best means of destroying the mites. 



Hydrocyanic acid gas also destroys red spider. 



Hops, melons, and cucumber are amongst outdoor plants 

 that suffer severely from the attacks of species of red spider. 



Gooseberry red spider. This mite often does serious injury 

 to gooseberry bushes by sucking the sap from the leaves, which 

 consequently results in early defoliation, the fruit also fre- 

 quently falling prematurely. Infested leaves are speckled with 

 ashy-grey, or altogether assume a leaden tinge. The mite is 

 known as Bryobia ribis (Thomas), and is distinguished from 

 the red spider of the vine, etc. {Tetranychus telarius), by its 

 larger size, and by the first pair of legs being much longer 

 than the rest. The colour varies from dull red to grey or 

 greenish. It does not spin a web. Like the other kinds of 

 red spider, this species is generally considered to be favoured 

 in its development and extension by dry, warm weather, 

 nevertheless during the remarkably wet season of 1909 the 

 gooseberry red spider was received in exceptional quantity 

 from different parts of the country at Kew for identification. 



Spraying thoroughly, as occasion requires, with a solution 

 of potassium sulphide is of service in checking the spread of 

 the mites. 



A fuller account of this and other mites attacking fruit- 

 trees will be found in Theobold's excellent book on The Insect 

 and other Allied Tests of Orchard, Bush, and Hothouse Fruits. 



