Order ACARINA 
Mites and ticks 
The order Acarina contains a large number of important pests 
of plants and man and animals. The majority are extremely small 
and seldom seen; others, such as the ticks, are large enough to 
be seen with the naked eye. Members of this order differ from 
other Arachinids in having the mouth parts more or less distinctly 
set off from the rest of the body on a false head and in never 
having the body so divided that a distinct cephalothorax and 
abdomen are clearly recognizable (18). 
MITES.—Numerous species of mites feed on and weaken or 
kill a wide variety of valuable plants, including trees. Many others 
attack man and various other forms of animal life, often causing 
extreme irritation, and sometimes illness and death. A consider- 
able number are either parasitic or predaceous on various species 
of destructive insects and harmful species of their own kind. 
Many others feed on dead materials of all kinds on the forest floor. 
The family Tetranychidae (480, 281) contains a large number 
of species commonly known as spider mites, many of which are 
important pests of trees and shrubs. These mites vary in color 
from yellowish, greenish, orangish, and reddish to red, and all 
are less than 1 mm. long. Infested leaf surfaces are usually 
covered with a fine netting of silk and spotted with tiny spherical 
eggs or broken egg shells. Heavily infested foliage may be dis- 
colored, disfigured, or killed. 
The spruce spider mite, Oligonychus ununguis (Jacobi), feeds 
on a number of conifers, especially spruce, cedar, and some of the 
pines and is widely distributed in the United States. Infested 
trees may become brownish-gray and appear unhealthy, or they 
may be completely defoliated. Outbreaks over large forested areas 
have been recorded. Periods of drought appear to be most favor- 
able for pepulation build-ups. Outbreaks have also occurred fol- 
lowing widespread spraying with DDT (403). Young nursery 
stock and recently planted trees are especially subject to serious 
injury. 
Oligonychus milleri (McG.) feeds on pines throughout the 
South and north to Pennsylvania and the Lake States. Out- 
breaks covering millions of acres have been recorded during 
recent years from North Carolina to Florida, in northern Louisi- 
ana and southern Arkansas, and in Mississippi and Texas. Young, 
Spee sown, even-aged stands appear to be susceptible to severe 
attack. 
Other important species in the genus Oligonychus include: (1) 
O. bicolor (Banks)—long recognized as a pest of oaks, especially 
shade oaks and sometimes injures beech; (2) the southern red mite, 
O. ilicis (McG.)—damages azalea and camellia; (8) O. aceris 
(Shimer)—sometimes a serious pest of maples; (4) O. letch- 
wortht Reeves—occasionally seriously injures hop hornbeam; (5) 
O. newcomert McG.—often seriously infests shadbush; (6) O. 
cunliffei P. & B.—feeds on longleaf pine in Florida; (7) O. bou- 
dreauxt P. & B.—feeds on cypress in the South; and (8) O. 
Bans P. & B.—feeds on oaks from Washington, D. C. to North 
arolina. 
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