24 BULLETIX 416, U. S. DEPARTMENT OF AGRICULTURE. 



several species of plants then bearing green leaves. Ewing (1914) 

 states that in Oregon the females enter the period of hibernation in 

 October, and. that males are not foimd during winter. 



At Batesburg we have repeatedly investigated hibernation. Old 

 cotton stalks, trash from in and around recently hif ested cotton fields, 

 dormant weed stalks, violet roots and crowns, and similar material 

 (gathered from locaUties of recent infestation) were collected durmg 

 winter and placed in a large Berlese apparatus. The results were 

 always negative. Many examinations have been made of dormant 

 cotton stalks and other plants which had, during the previous season, 

 harbored mites. We have never recovered living red spiders from 

 these dormant hosts. In short, there is absolutely no evidence which 

 would lead to the behef that hibernation occurs in South Caroluia. 

 The pest maintams itself throughout the winter on several species of 

 wild and dooryard plants. We have traced infestation through four 

 successive years, from the primary sources to cotton fields and back 

 to the wintermg hosts, and have estabhshed the botanical sequence 

 which constitutes the successive migratory steps of seasonal activities. 



The cUspersion of the pest is determined largely by the nature and 

 location of the plants upon which the mites overwinter. These hosts 

 are divisible into summer hosts and winter hosts. Under summer 

 hosts we place such species as harbor mites through the summer and 

 which remain green throughout the winter, thus furnishing continu- 

 ous feeding during all months of the year. Hosts of this kind are of 

 vast importance in that they obviate the necessity of fall migration 

 on the part of the mites. Among the more important plants of this 

 type are the cultivated violet, strawberry, hollyhock, mustard, privet, 

 and grass {Panicum scoparium). It is probably true that compara- 

 tively few infestations in cotton arise directly from these summer 

 hosts. The balance of the mites persist through winter on the winter 

 hosts. These mclude the native weed species which germinate or 

 put out basal leaves in the fall, and to which a certain percentage of 

 the migrants, from cotton and other annual plants, disperse. Where- 

 ever these weeds are allowed to grow in great profusion they are 

 usually found to be infested, and when occupying positions close to 

 cotton fields they constitute centers of direct invasion. Among the 

 more common of the winter hosts in South Carohna are Stachys 

 arvensis, Geranium carolinianum, Rubus sp. (wild blackberry), CJieno- 

 f odium hotrys, Sonchus asper, and Oenothera laciniata. Since the great 

 mass of red spiders pass the winter on the wild plants, it is evident 

 that these plants are of great importance. They occur commonly in 

 dense borders along ditch banks, in field borders adjoining areas 

 planted to cotton, in dooryards, and bordering roadsides. 



Practically all of the winter hosts possess only prostrate leaves 

 during the late fall and winter. This makes the foUage more acces- 



