abdomen. The body of a full-grown specimen is about 12 mm long exclusive of the 
long legs. Males are much smaller and are seldom seen. 
The brown recluse spider, Loxosceles reclusa Gertsch and Mulaik, is also quite 
poisonous to humans, its bite producing a condition known as “North American 
Loxoscelism.” Adults are about 9 mm long, have long legs, and vary from light 
fawn to dark brown. A distinguishing mark is a dark fiddle-shaped band on the 
anterior portion of the carapace, which narrows to a thin center line and extends 
almost to the abdomen. It is only within recent years that this species has been 
recognized as poisonous to humans. It has been recorded from the Southern and 
Central States. It may be found in almost any location where protection, food, and 
dryness are adequate, but it probably occurs most commonly inside buildings. Its 
web is medium-size and irregular, with a maze of threads extending in all directions 
without definite pattern (573). 
It is usually impractical or impossible to eliminate spiders completely. Popula- 
tions can be reduced, however, by the removal of favorite breeding places. 
Order Acari—Mites and Ticks 
The order Acari contains a large number of important pests of plants, humans, 
and other 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 arachnids in having the mouth parts more or less distinctly set off 
from the rest of the body on a false head, and the body is never so divided that a 
distinct cephalothorax and abdomen are clearly recognizable (39). 
Mites.—Numerous species of mites feed on and weaken or kill a wide variety of 
valuable plants, including trees (640). Many others attack humans and various other 
forms of animal life, often causing extreme irritation, and sometimes illness and 
death. A considerable number are either parasitic or predacious on various species 
of destructive insects and harmful species of their own kind (750, /076). Many 
others feed on dead materials of all kinds on the forest floor. 
The family Tetranychidae (465, 7S/) contains a large number of species com- 
monly known as spider mites, many of which are important pests of trees and 
shrubs. These mites vary from yellowish, greenish, orangish, and reddish to red, 
and all are less than | 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 discolored, disfigured, or killed. 
The spruce spider mite, Oligonychus ununguis (Jacobi), feeds on a number of 
conifers, especially spruce, thuja, and some of the pines, and is widely distributed 
in the United States. Infested trees may become brownish gray and appear un- 
healthy, or they may be completely defoliated. It is considered the most destructive 
conifer-feeding mite known (/43). Outbreaks over large forested areas have been 
recorded. Periods of drought appear to be most favorable for population buildups. 
Outbreaks have also occurred following widespread spraying with DDT (642). 
Young nursery stock and recently planted trees are especially subject to serious 
injury. 
Oligonychus milleri (McGregor) feeds on pines throughout the South and North 
to Pennsylvania and the Lake States. Outbreaks covering millions of hectares have 
been recorded from North Carolina to Florida, in northern Louisiana and southern 
Arkansas, and in Mississippi and Texas. Young, open-grown, even-aged stands 
appear to be susceptible to severe attack. 
Other important species in the genus Oligonychus include O. bicolor (Banks), 
long recognized as a pest of oaks, especially shade oaks, and sometimes injurious 
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