30 BULLETIN 416, U. S. DEPARTMENT OF AGRICULTURE. 
TaBLe V.—List of important spring weed hosts of the red spider, Batesburg, S. C. 
Stachys arvensis. Rumer crispus. 
Chenopodium botrys. Stellaria sp. 
Sida rhombifolia. Solanum carolinense. 
Geranium carolinianum. Solanum nigrum. 
Trifolium repens. Ipomoea purpurea. 
Sonchus asper. Passiflora incarnata. 
Viera sativa. Lechea villosa. 
Taraxacum officinale. Brassica campestris. 
Gnaphalium spathulatum. Wild grass. 
Rumex obtusifolius. Rubus sp. 
Oenothera laciniata. _ Phytolacca americana. 
Oxalis stricta. Ambrosia artemisiaefolia. 
Panicum scoparium. Amaranthus hybridus. 
Helianthus annuus. Datura stramonium. 
Convolvulus sp. Erigeron sp. 
Plantago lanceolata. Xanthium americanum. 
Croton texensis. 
WATER DISPERSAL. 
For a long time investigators of the red spider found it difficult to 
explain why isolated infestations existed in fields comparatively 
remote from the source of dispersion. It has been known for years 
that heavy rains dislodge many red spiders, and it has been taken 
for granted that these mites were destroyed. We have established 
the fact, however, that 9 hours’ submergence in water is necessary to 
cause the death of red spiders. Beaten to the ground by the heavy 
downpour of rains, countless thousands of mites are carried along in 
the surface water and may even find their way into the smaller 
creeks. Provided the red spiders are not injured, they may revive 
and become established many rods, perhaps, from the scene of 
detachment. Table VI presents the data on submergence of mites 
and the resulting mortality. 
TaBLE VI.—Submergence and red spider mortality, Batesburg, S. C., 1914. 
| | 
E an d f | E ere cond f 
xperi- : va Condition of in- xperi- 4 va | Condition of in- 
rier Ex- before ee dividuals not ment = before As | dividuals not 
No. posure. oxami- ye) recovering. No. P ®- | exami- | y: recovering. 
nation. | ‘nation. | 
aee er Per 
Hours.| Hours.| cent. | Hours. | Hours.| cent. 
De Tate iee 24 | 12] 100) Macerated. iN ep ene 12 4 100 | Shrunken 
De oh ios ae 24 12 | 100 | Do. PS ey 9 3 100 Do. 
PP enGa EA 24 3 100 | Shrunken. Tees cae 10 6| 100 | Macerated 
yee aie 24 3 100 Do. Mae ee So 8 11.5 6; 100 Do. 
Bee ee 12 2 100 | Do. pirate 5 10} 50 | Do. 
Ge op. aes 7 15 170 | Macerated. ie Se ee 8. 25 4 83 | Shrunken. 
(aR ae 25 4 | 0 | Wiens 10. 25 6 | 195.3 | Macerated. 
Bese. 17.5 5 | 100 | Shrunken. ages | 9 4; 100 Shrunken. 
a gens ee 8 6 50 | Shriveled. 19. eee3 any 8 95 Macerated. 
de eee 10 6 
100 | Shrunken. | | 
1 A minute air bubble, about which were some of the mites, remained in the vial. 
