32 BULLETIN 416, U. S. DEPARTMENT OP AGEICULTURE. 



ground and 650 feet from the infested orchard. All of these tests 

 were made at tnnes when the usual light summer winds were blowing. 



We conducted similar tests at Batesburg and were able to corrob- 

 orate to some extent the results of Munger. In one test we suspended 

 by a string a board bearing on each side two sheets of sticky fly paper. 

 The trap board was then attached to a wire stretched between poles. 

 A sticky substance was smeared on the suspending string to prevent 

 the mites from reaching the sticky surface by crawling. The sus- 

 pended board was free to swing in any direction, so that mites being 

 borne by the wind from any direction would be intercepted. An 

 orange tree which harbored Tetranychus mytilaspidis stood about 300 

 feet from the exposed sticky surface, and several other host plants 

 infested with T. himaculatus grew within 20 to 25 feet. After an 

 exposure of 36 hours the sticky paper was examined. Ten adult 

 specimens of T. mytilaspidis and several immature individuals of T. 

 himaculatus were caught. 



During the periods of drought and food scarcity mites have been 

 seen to seek the highest or terminal points of branches, and this habit 

 of the red spider may be closely associated with dispersion by wind. 

 Naturally, this act would bring them to points where the effect of 

 the wind would be greatest. 



OTHER DISPERSION AGENCIES. 



Several additional agencies have been suggested by various writers 

 as means of spread of the red spider. The operation of cultivating 

 the crop has long been considered to be instrumental in conveying 

 mites from point to point about cotton fields. Titus (1905) main- 

 tained that the members of hoe gangs and cultivators are the most 

 common means of distribution. He claimed that mites cling to any 

 substances that brush against them, and in this manner are rapidly 

 and thoroughly scattered over fields. The effect of distribution along 

 rows and across fields, following the routes taken by farm hands, can, 

 he claims, be traced easily by the resulting infestation along these 

 routes. The present writers are inclined to minimize this acci- 

 dental type of dissemination. Even when manipulated with the 

 finest camel's-hair brush a certain percentage of individuals are 

 kiUed. 



Alhed with this form of dispersion is that of accidental transpor- 

 tation by larger insects. Titus states that mites have been taken 

 from several insects, such as grasshoppers and small Hemiptera, 

 which often visit cotton plants. Such agencies of dispersion as in- 

 sects, domestic animals, poultry, and wild birds should be considered 

 as being of minor importance. 



