4 BULLETIN 416, U. S. DEPARTMENT OF AGRICULTURE. 
FOOD PLANTS. 
As the result of the investigations at Batesburg, S. C., supple- 
mented by observations throughout the cotton belt, this mite has been 
taken from 183 species of plants, including weeds, ornamentals, and 
garden and field crops. Upon most of these the pest has been seen 
only occasionally, but it is found commonly throughout the active 
season upon the following plants: Cotton (Gossypium spp.), cultivated — 
violet (Viola spp.), (Pl. IV, fig. 4), Jerusalem oak (Chenopodium — 
botrys), wild blackberry (Rubus spp.), wild geranium (Geranium spp.), 
ironweed (Sida rhombifolia), garden bean (Phaseolus spp.), pokeweed 
(Phytolacca americana), tomato (Lycopersicon Lycopersicon), dahlia 
(Dahlia spp.), (PI. IV, fig. 3), sweet pea (Lathyrus odoratus), (Pl. IV, 
fig. 5), and hollyhock (Althaea rosea). 
Of these 183 host plants, 100 (or 55 per cent) are cultivated species 
and 83 (or 45 per cent) are native wild species. It should be stated, 
however, that in the preparation of this host list more time was 
devoted to house yards than to rural localities. Itseems reasonable — 
to suppose, therefore, that the common red spider occurs on fully as 
many wild plants as on cultivated species. The fact that Harvey’s 
(1892) 37 host plants reported from New England, and Ewing’s 
(1914) 30 hosts from the Northwest are practically all cultivated 
species may be accounted for by presuming that these investigators 
did not extend their research to the wild plants. 
Throughout the past five years of the red-spider investigation it has 
been brought to our attention repeatedly that certain plants possess 
a peculiar importance due to their restriction to certam seasons; 
hence they may thus form a series of links in the cycle of infestation. 
The cultivated violet, which has come to be recognized as perhaps 
the most important wintermg host, and as a source of dispersion to 
neighboring weeds and near-by cotton in the spring, is probably the 
most commonly infested plant in the South. 
The pokeweed (Phytolacca americana) occupies an important posi- 
tion as a host, but its exact status has never been clearly determined. 
Among farmers in various parts of the cotton belt there is a strong 
_ belief that red-spider infestation, called by them ‘“‘rust,’’ has its 
origin in pokeweed. The result of much careful study durmg the 
winter and early sprmg months seems to refute the idea that poke- 
weed normally supports mites during these periods. It does, how- 
ever, function as a very desirable secondary host during the early 
season migratory movements of the mites by intercepting a few indi- 
viduals. These intercepted mites multiply rapidly, until the poke- 
weed no longer furnishes sufficient nourishment, and at such times 
the infestation spreads to cotton if it is available. (PI. V, fig. 6.) 
Native blackberry vines also constitute an important overwinter- 
ing host, since many of the leaves remain attached throughout the 
ch 
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