45 



THE CLOVER MITE. 



{Bryohia pratensia Garman.) 

 By C. V. Riley and C. L. Marlatt. 



The subject of this article has been referred to several times in Insect 

 Life in extracts from correspondence, notes, and otherwise, but no full 

 account of it has been given. Occasion is now taken to place on record 

 the notes accumulated by the Division relating to its distribution and 

 habits together with such recommendations as to remedies as past ex- 

 perience warrants. Bryobia pratensis belongs to the family of vegetable- 

 feeding mites, Tetranychid.ne, which includes the well-known Eed Spider 

 of hot-houses and the Six spotted Mite of the Jrange, which was de- 

 scribed and figured in the annual report of the Entomologist for 1889. 

 It occurs very commonly in the Northern and Central States from 

 Massachusetts to California, and is especially annoying on account of its 

 habit, frequently developed in spring and autumn, of migrating in enor- 

 mous numbers into houses. No specimens have been received from the 

 Southern States, but the fact that it is abundant about Washington 

 would lead us to expect its occurrence farther south. 



The wide distribution of the species might lead to the supposition 

 that there were several distinct species ; but a careful examination of 

 the large series of specimens in the national collection shows no other 

 differences than in size and coloration, such as may be found in speci- 

 mens on a single piece of bark or leaf and which are chiefly due to 

 varying degrees of maturity. 



This Bryobia, from a general resemblance in habit, shape, and color 

 (particularly in its younger stages) to the Eed Spider of hot-houses, was 

 at first confounded with the latter species, which also, as is well known, 

 occurs not infrequently on trees and plants out of doors. In our earlier 

 notes we referred to it, therefore, as the red spider (Tetranychus tela- 

 rius) ; and, in the published writings of others concerning the occur- 

 rence of this last species out of doors, both mites have doubtless been, 

 in like manner, confused. 



This mite was first characterized scientifically in 1885 by Mr. H. Gar- 

 man in Forbes's Third Report, pages 73, 74, under the name given above, 

 which description is given at the close of this article. The species de- 

 scribed in the same place by Mr. Garman as B. pallida is evidently but 

 an immature form of B. pratensis. (concerning this Bryobia Professor 

 Forbes reported the following : 



At Normal, early in May, the general occurrence of a large and conspicuously 

 brownish-red mite was noticed upon clover and blue-grass, the former of these plants 

 especially, sometimes suffering severely from the pest. The leaves of the clover turned 

 yellow, and their growth was arrested where the mite was abundant. The effect on 

 the blue-grass was similar. 



