THE RED SPIDER ON COTTON, 29 
Rate of travel.—tin order to ascertain the rate of movement of 
wandering red spiders a series of laboratory experiments was con- 
ducted. A large sheet of coarse wrapping paper was fastened tightly 
ona4by6 table. The red spiders to be tested were liberated at the 
center and their progress was traced for periods varying from 5 to 
90 minutes. 
The influence of temperature on the rate of travel was very marked, 
and was established by conducting the foregoing tests on both hot 
and cool days. It also develops that the average rate of travel by 
the female red spider in summer is 4.82 inches per minute, while that 
of the male under similar conditions is 2.95 inches per minute. (See 
Table IV.) 
SOURCES OF DISPERSION. 
When cotton fields occur in urban localities it often happens that 
infestations arise directly from garden or dooryard plants, such as 
the violet, sweet pea, dahlia, hollyhock, garden bean, etc. (PL. IV, 
figs. 3-5; Pl. V, fig. 4.) As has been pointed out, however, the pest 
more usually reaches cotton in the course of a series of migrations, 
beginning with the primary hosts as foci, and advancing from host to 
host as the native species appear above the ground in spring. The 
plants which so happen to harbor the pest in situations adjacent to 
cotton, when the latter appears, become the immediate sources of 
dispersion to the cotton field. 
Weed borders (PI. V, fig. 5), which have been known to give rise 
to very acute infestations in adjoining cotton fields, and which pre- 
vail throughout the entire year, have been made the subject of con- 
tinued observation, with the result that the position of such weeds 
in the problem is now quite clearly understood. There are certain 
weed species that at times occur in almost pure growths; that is, 
countless thousands of seedlings of a given species may grow in con- 
tinuous, dense borders. This was often noticed at Batesburg, where 
at times weed infestation became so acute that entire borders of 
Geramvum .carolimanum, Stachys arvensis, etc., wilted, and finally 
succumbed entirely. It is just such cases as these that produce a 
migration of red spiders to the cotton fields. A rather complete list 
of the native plants at Batesburg which are of great importance in 
advancing the red spider to cotton in the spring is given in Table V. 
