THE RED SPIDER ON COTTON. 



insects have been observed ensnared and dead among the fibers. New 

 females, after mating, either select an attractive spot on the leaf, 

 or migrate upward to a more tempting leaf, or, as frequently is the 

 case when overcrowded, travel to another plant. 



THE VIOLET AND POKEWEED AS HOSTS. 



When cotton dies or becomes untempting in the late fall an exodus 

 of red spiders from the cotton fields occurs in the effort to find more 

 suitable food plants. At this time cotton mites may be easily found 

 on a number of native and cultivated plants, prominent among which 

 are cowpeas, tomato, Jamestown weed, ironweed, pokeweed, and cul- 

 tivated violets. Most of these plants die after the frosts, but poke- 

 weed furnishes considerable green tissue beneath the ground level, 



and the violet remains somewhat green 

 throughout the winter. Out of many 

 cases of cotton infestation investigated 

 during the last two seasons the vast 

 majority of them have indicated 

 most clearly that the original source 

 of the pest was either the English 

 violet (figs. 2, 3) or pokeweed {Phyto- 

 hicca decmvdra) (fig. 4). 



Practically all occurrences in urban 

 localities have been intimately associ- 

 ated with cultivated violet plants and 

 doubtless originated from them. On the 

 other hand, with very few exceptions 

 rural cases of infestation are traceable 

 to pokeweed stalks growing at the 

 field borders or on the terraces. The 

 description of a rural occurrence at 

 Allendale, S. C, will serve to illustrate a typical case of origin from 

 pokeweed. In this instance the infestation was seen to grow increas- 

 ingly severe as one approached a certain point on a terrace. Con- 

 verging from all directions toward this center, infestation clearly 

 became heavier until an area was reached where the plants were de- 

 nuded of foliage. Precisely in the center of this area there grew a 

 large pokeweed stalk. It was " alive " with mites and was lightly 

 festooned with their webbing. 



It is not yet entirely clear in what manner the red spider passes 

 the winter on pokeweed. The plant is a perennial, and the stalks die 

 to the ground in the late fall. Just below the soil surface, however, 

 the soft fleshy roots, which are succulent, begin (fig. 4). In addition, 

 at the crown of the root, at about the ground level, there are always 



Pig. 2. — Diagram showing how vio- 

 lets growing in dooryard give 

 rise to red-spider infestation in 

 adjoining field. The infestation 

 is most severe near the yard. 

 This diagram is typical of many 

 cases found during 1911. (.Au- 

 thor's illustration, i 



