INSECT ENEMIES OF WESTERN FORESTS 



67 



sects. Aphrophora permutata Uhl. sometimes injures Monterey 

 pine and is also found on other pines, spruces, and firs in all the 

 Western States. Other species of Aphrophora and Clastoptera are 

 found on other forest trees in the West. 



Figure 28. — The irregular pine scale (Toumeyella pinicola) on Monterey 

 pine twigs. Slightly enlarged. 



SPIDER MITES 



Spider mites constitute a group of arthropods that have sap- 

 sucking habits (A7). These are not insects, but belong to the same 

 group as spiders (Arachnidae). They have bodies divided into 

 two segments instead of three, and have four pairs of legs instead 

 of three. However, since they are closely related to insects and 

 their work is similar, they are considered in this discussion. 



These tiny spider mites have sharp-pointed, piercing mouth 

 parts with which they suck the juices from leaves and tender 

 stems of various plants, including many ornamental, shade, and 

 forest trees. Leaves turn yellow and drop or are covered with 

 silvery patches or webs. Peculiar galls are sometimes formed by 

 these mites. Heavy attacks seriously weaken, and sometimes kill, 



