14 



THE RED SPIDEE ON COTTON. 



imything which can be done by man during the season. From obser- 

 vations made, both early in the season and at the beginning of win- 

 ter, it is doubtless true that the young stages are killed by freezing 

 ■weather. This naturally prevents any considerable winter increase, 

 and in addition some adults probably perish. 



The influence exerted upon the red spider by preseasonal condi- 

 tions appears to be even greater than that of the factors operating in 

 summer weather. The winter of 1911-12 was the severest in South 

 Carolina for many years. Hence it might be expected that the fol- 

 lowing season would be a mild one. from the standpoint of injury 

 by the red spider, through the assumed heavy mortality of the pest 

 during the winter. On the contrary, as has been stated before, the 

 1912 occurrence was the severest on record. The only possible ex- 

 planation appears to em- 

 brace two suppositions. 

 One is that the adult red 

 spider is little susceptible 

 to extreme cold. The 

 other is that the insect 

 enemies of the mites suc- 

 cumb much more easily 

 to minimum temperatures 

 than do the mites them- 

 selves. Both of these hy- 

 potheses are sustained by 

 all observations of the 

 writer. Naturally, then, a 

 severe Avinter is precisely 

 what would most favor 

 the subsequent increase of 

 the red spider through the destruction of its insect enemies. Con- 

 versely, an abnonnally mild winter, free from decidedly low tempera- 

 tures, should furnish conditions most favorable for the survival of 

 the repressive species, and the infestation for the following season 

 would be mild. 



INSECT KNEMIES. 



Fio. 10. — Arihrociioda.r sp.. a predaceous enemy of 

 the red spider. At left, mature predaceous larva, 

 ma^ifled 00 times : at right, adult female, ^jreatly 

 enlarged. (Original.) 



Hot weather, although favoring red-spider development, probably 

 encourages even more the increase of insect enemies, of which sev- 

 eral have been observed. Were it not for these inconspicuous friends 

 of the farmer the depredations to his crops by the red spider would 

 unquestionably be more severe. The following are a few of the 

 more important beneficial species observed during the .season of 1912 

 at Batesburg, S. C. 



