36 BULLETIN 416, U. S. DEPARTMENT OF AGRICULTURE. 
Plate VIII is a diagram which, to some degree, graphically indicates 
the complex relation which the red spider bears to its environment. 
In a number 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 mfested 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 macropilis 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. 
Rhyncholophus pilosus Banks.—This species was observed at 
Batesburg destroying the red spider on ‘‘mare’s tail’? (Lechea 
villosa) and on Boston ivy. 
ANYSTIDAE. 
Anystis agilis Banks.—This mite (fig. 9) is frequently seen crawling 
about in unlikely places in 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 (Sambucus sp.) 
at Batesburg, but have made no accurate estimate of its control 
value. Ewing reports finding considerable numbers of this mite 
upon violets, heavily infested with red spiders, in Oregon. 
