THE RED SPIDER ON COTTON. oi 
weather are almost certain to perish with the return of lower tem- 
peratures. : 
Variation vn abundance from year to year.—lt is noticeable that the 
degree of occurrence varies greatly from year to year. We find 
from a study of the various natural influences that it is possible to 
foretell the probable status of the pest during a given season with 
considerable assurance. The red spider is extremely resistant to 
adverse meteorological conditions, and no matter how severe the 
winter, a considerable proportion of the mites come through safely. 
On the other hand, many of the insect species which are predatory 
upon the red spiders, being of a more susceptible nature, are less 
likely to survive the hardships of a severe winter. Theoretically, 
after a mild winter there should be an abundance both of mites 
and predators, while after a severe winter the mites should survive 
in a much greater proportion than their enemies. This condition 
has obtained during the past four years, mild winters being followed 
by mild red-spider seasons, while severe winters have been followed 
by seasons of heavy mite occurrence. 
DISPERSION. 
When the food supply on favorable host plants becomes exhausted 
dispersion to new food plants takes place, and it is usually by a 
succession of such dispersions that cotton finally becomes infested. 
Ground travel.—On many occasions red spiders have been observed 
crawling on the ground in the vicinity of grossly infested plants, fre- 
quently crawling up and down the stems in search of more favorable 
hosts upon which to feed. In order to ascertain whether red spiders 
leave the plants of their own volition and crawl upon the ground 
in attempts to extend their range, the following experiment was 
instituted. — 
Tests of red-spider movements.—Large sheets of sticky fly paper 
were carefully fitted about the bases of cotton stalks. The sticky 
surfaces were permitted to remain in this position for periods varying 
from 24 to 48 hours. At the conclusion of these exposures careful 
examinations were made, of which the following specific results are 
rather typical: Five red spiders were observed on the inner edge, 
which came in contact with the base of the stalk; 29 mites were 
caught on the extreme outer edge, which was flush with the finely 
packed soil; 5 red spiders were found ensnared at dffferent points 
in the central area of the sticky surface. The only possible deduc- 
tion is that the first-mentioned 5 individuals were intercepted as 
they were descending the stem; that the 29 mites were trapped as 
they were crawling over the ground surface, presumably toward the 
cotton stalk; and that the last-mentioned 5 undoubtedly dropped 
directly from the overhanging foliage. 
