August, '14] McGREGOR: RED SPIDER CONTROL 325 



different from those commonly obtaining in the reahn of insect pests. 

 This, moreover, is found to be the case. The red spider is a gregarious, 

 non-flying, non-hibernating, suctorial, phytophagous pest. It differs 

 from the typical insect pest in that it remains active through the 

 ■uinter, is incapable of dispersion by flight, and in the limitation of the 

 individual in its feeding operations, practically, to the immediate 

 scene of its birth. The red spider, then, from the standpoint of bio- 

 logical characteristics, is to be likened most, perhaps, to the homop- 

 terous Hemiptera as a group and, naturally, the direct combative 

 measures employed against the mites are somewhat similar to those 

 used against such families, for example, as the Aphididse and Coccidse. 



The absence of flight in the case of the red spider is a factor working 

 gFeatly to the advantage of the agriculturist. It is a handicap against 

 rapid dispersion which, try as it 3iay, can never be overcome by the 

 group. The means of spread are chiefly three: — first, through the 

 agency of accidental transportation by other creatures; second, by the 

 actual locomotion of the indiA'iduals themselves; and third, by hydro- 

 locomotion. 



It has long been recognized that larger insects, birds, domestic 

 animals (especially plow animals at the time of cultivation), etc., 

 served occasionally to transport mites from plant to plant. This, 

 however, I do not consider a potent factor in the serious spread of the 

 pest. It has likewise been observed that red spiders travel from plant 

 to plant along branches which are in contact with one another. ]\Ir. 

 Worsham,in his bulletin on the subject, emphasized this method as the 

 only means of spread which he observed. It has been determined in 

 South Carohna, however, that mites also travel on the ground from 

 stalk to stalk, the average rate being about one inch per 15 seconds. It 

 appears estabUshed, though, that the great bulk of continuous dis- 

 persion is effected mainly by means of travel from plant to plant across 

 the interlacing branches. 



It had been difficult until this year to explain, however, in what 

 way isolated spots of infestation came to exist in fields rather remote 

 from the presumed source of dispersion. Observations conducted the 

 past season at Batesburg, S. C, by Mr. McDonough and myself, have 

 brought to light a new tyY)e of dispersion which seems unique, and we 

 have called it hydro-locomotion. This factor easily accounts for most 

 cases of sporadic infestation. It has been known for j^ears that heavy 

 rains are effective in washing off manj'' red spiders to the ground. It 

 was taken for granted that these washed-off mites were thus destroyed 

 and eliminated for all time. It is known now, however, from experi- 

 ments of the past season, that nine hours complete submergence is 

 necessary to insure the death of the red spiders by water. The appli- 



