36 BULLETIN 416, U. S. DEPARTMENT OF AGETCULTUEE. 



Plate VIII is a diagram which, to some degree, graphically indicates 

 the complex relation which the red spider bears to its environment. 

 In a nmnber of instances these predatory species also operate against 

 other small insects, such as aphids, scale insects, mealy bugs, white 

 flies, etc. So far as is known, only two predators are enemies exclu- 

 sively of the red spider, namely, the two midges. One predatory 

 species, the cotton leafworm (Alabama argillacea), is only incidentally 

 an enemy of red spiders, through the fact that myriads of 

 mites are devoured along with the cotton foliage. This defoliation 

 occurs generally over the cotton belt from time to time. Two of the 

 predators, in turn, become enemies of other predators as well as of 

 the mites. The most heavily parasitized of the predators are the 

 chrysopids and the syrphids, the mortality of which becomes rather 



high at certain times. 



arachnida, acarina. 



Gamasidae. 



Seius quadripilis Banks. — This mite was collected by Mr. G. A. 

 Runner at Key West, Fla., on a wild grass infested with the red 

 spider, and also at Orlando, Fla., on infested chinaberry leaves by 

 Mr. W. W. Yothers. Its abundance at these localities suggests that 

 it probably exerts considerable control. 



Macrocheles sp. — This mite has been found on pokeweed (Phyto- 

 lacca americana) heavily infested with the red spider at Batesburg. 

 It has been observed actively at work in mite colonies, and is doubt- 

 less of economic value. 



Laelaps Tnacropilis Banks. — Mr. J. D. Mitchell found this mite on 

 two occasions at Victoria, Tex., where it was doing good control 

 work on heavily infested sweet peas. Mr. W. W. Yothers also sent 

 it on badly infested chinaberry leaves from Orlando, Fla., where 

 the species was responsible for the marked decimation of the red 

 spider which occurred in the late summer. This mite is an important 

 enemy of the red spider. 



Rhyncholophidae . 



RTiyncTiolopJius pilosus Banks. — This species was observed at 

 Batesburg destroying the red spider on "mare's tail" (LecTiea 

 villosa) and on Boston ivy. 



Anystidae. 



Anystis agilis Banks. — This mite (fig. 9) is frequently seen crawling 

 about in unlikely places m search of food. It is extremely active and 

 follows a tortuous course that sooner or later brings it to its victims. 

 We have collected it from mite-infested elderberry (Samhucus sp.) 

 at Batesburg, but have made no accurate estimate of its control 

 value. Ewing reports fuiding considerable numbers of this mite 

 upon violets, heavily infested with red spiders, in Oregon. 



