INSECT ENEMIES OF WESTERN FORESTS 51 
Other common scales infesting western coniferous trees include the 
following: 
Species Hosts 
Matsucoccus fasciculensis Herbert__ Ponderosa and digger pines. 
Toumeyella pinicola Ferris (fig. 23)_- Monterey pine and other pines in California. 
Physokermes insignicola Craw __-_- Monterey pine. 
Physokermes concolor Cole________ White fir. 
Physokermes coloradensis Chiltaes: slue spruce in Colorado. 
Aspidiotus ehrhorni Cole_2----____- Douglas fir and cypress in California. 
Ehrhornia cupressi Ehrh. (41)--__ Monterey cypress. 
Xylococcus macrocarpac Cole-—_—_—_. Monterey cypress. 
AGHLOLa shastae Coles -—- Bigtree in California. 
Some of the mealy- 
bugs also attack for- 
est trees. ‘These are 
small, soft-bodied 
bugs covered with a 
white powdery wax. 
They are represented 
by Pseudococcus ry- 
ani Coq. on cypress, 
incense cedar, and 
redwood, and P. se- 
gquoiae Cole on red- 
wood. 
The foregoing is 
only avery brief and 
incomplete treatment 
of the scales and re- 
lated insects which 
may be found attack- 
ing forest trees, since 
the species attacking 
various broadleaved 
trees (42) are too 
numerous to mention 
here. 
SPIDER MITES 
Another group of 
small animals of sap- 
sucking habits is TOR na 
(Mie oteeseben ge ole 9 2 71G paiawonterey ‘pine twice” Natural sie) 0 
mites. Strictly 
speaking, these are not insects, since they have bodies divided into 
two segments instead of three and have four pairs of legs instead of 
three. However, since they are so closely related to insects, and their 
work is so similar, they are considered in this discussion. The dam- 
age resulting from their natural habit of sucking the juices from 
leaves and tender stems of various plants, including many orna- 
mental, shade, and forest trees, is considerable. The leaves turn 
yellow and drop, and the trees attacked are often seriously weakened, 
rendering them susceptible to attack by tree-killing insects. This 
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