THE BED SPIDER ON COTTON. 



23 



rearing cells attached close to the ground quicker development 

 residted than in those attached liigher on the plant. As this arises 

 through heat reflection from the soil, the rearing cells were attached 

 usually at points 3 or 4 feet from the ground in order to ehminate this 

 surface radiation in so far as possible. 



SEASONAL HISTORY. 



Over-wintering Jiahits. — Several European writers have stated 

 that the common red spider of the Continent passes the winter in a 

 state of hibernation under bark scales or in the ground. Duges 

 found this species under stones 



and concluded that they reached 

 the gromid with the falhng 

 leaves. Von Hanstein (1902) 

 found them during the winter in 

 large numbers in the ground 

 near trees wliich had been se- 

 verely infested. He states that 

 mites are often so thick about the 

 c^o^^^l of the tree roots that 

 when the soil is removed they 

 become plainl}^ visible from some 

 Httle distance, and adds that the 

 red spiders fashion wintering 

 quarters in the protective crev- 

 ices of the bark. In Colorado, 

 Weldon (1909) determined that 

 the -vvinter is spent in the ground, 

 and states that myriads of red 

 spiders were found below the soil 

 surface at the crowns of trees 

 upon which they had been feed- 

 ing. Some were found at a dis- 

 tance of 10 feet from the trees, 

 where they had crawled beneath 

 clods of soil to hibernate. Weldon states that hibernation begins before 

 the cold weather sets in, the first downward migration of mites occur- 

 ring toward tlie end of July. Wilson (1911) (Batesburg, 1910) enter- 

 tained the belief that the red spiders overwinter on cotton plants near 

 the base of the stalk, and was certain that they hibernate about the 

 roots of cultivated violets. Worsham (1910) seems to have been the 

 earliest investigator to recognize the fact that in the Southeast, at 

 least, the red spider passes the winter actively in the adialt stage, 

 and even propagates sparingly at temperatures slightly a])ove 

 freezing. lie found small colonies housed during the winter on 



Fig. 7. — Type of isolation cell employed for the 

 life-history and other developmental studies of 

 the red spider. Attached to violet leaf. (Orig- 

 inal.) 



