8 THE RED SPIDER ON COTTON. 



to yards with borders of violets. Large fields are probably never 

 completely damaged, but small fields frequently become wholly 

 affected. The crop of one 5-acre field near Leesville, S. C, was 

 probably reduced at least 50 per cent by this pest. Local spots with 

 from 25 to 100 per cent damage are frequently to be seen. 



NATURAL CONTROLLING AGENCIES. 



Red spider occurrence was most severe throughout July and was 

 still at its height on August 1. Within three weeks of the latter 

 date, however, the pest had become so greatly diminished that it was 

 hardly noticeable and was doing practically no damage. This 

 phenomenon indeed happened suddenly, and the agencies which 

 worked to produce it are unquestionably of great economic value. 

 The toughening of the leaves at that time may have caused many 

 mites to desert cott6n for other plants, but another factor of much 

 more importance was the appearance in abundance of several species 

 of insect enemies. 



CLIMATIC INFLUENCES. 



As before mentioned, climatic conditions exert a marked influence 

 upon the welfare of the pest. During times of little rainfall and 

 high temperature reproduction goes on by leaps and bounds; on 

 the other hand, long, heavy rains work havoc to the red spider 

 population. In spite of the fact that the red spiders inhabit the 

 underside of the leaves, many are washed off by rains and many more 

 are destroyed by the upward bombardment of sand particles, which 

 ma}'^ always be seen coating the lower leaves after storms. From 

 observations made both early in the season and at the beginning of 

 winter it is doubtless true that the young stages are killed by freez- 

 ing weather. This naturally prevents any considerable winter in- 

 crease, and in addition many adults probably perish. 



INSECT ENEMIES. 



Hot weather, although favoring red-spider development, also en- 

 courages the increase of insect enemies, of which several have been 

 observed. AYere it not for these inconspicuous friends of the farmer 

 the depredation to his crops by the red spider would unquestionably 

 be far more severe. The following are a few of the more important 

 beneficial species observed this season at Batesburg, S. C. 



Triphleps insidlosKs Say (fig. 4), a small anthrocorid bug, was 

 seen from the beginning of August, and both in the nymphal and 

 adult stages was probably the most effective enemy of the spider. 

 Coming upon a red spider like a flash, the adult thrusts its sharp 

 proboscis through the pest's back and proceeds quietly to siphon out 



