INSECT ENEMIES OF WESTERN FORESTS 69 



Key to Recognition of Some Important Insect Galls 



A. Galls formed on coniferous trees. 



1. Galls on pines. 



a. Affecting pine needles. 



(1) Needles greatly enlarged or swollen at the base 



Gail midges, p. 70 



(2) Needles aborted or blistered within the sheaths, 



causing premature shedding. . . .Pine bud mite, p. 69 



b. Affecting pine twigs. 



(1) Swollen twigs covered with gray, cottony secre- 



tions Chermes, p. 58 



(2) Twigs with dying and dead needle tufts 



("flagging"). 

 aa. Bark filled with resinous pockets, or 

 exuding small resinous masses, con- 

 taining small red maggots 



Pitch midges, p. 70 

 bb. Bark swollen or cracking open; small 

 brown scales in bark crevices 



Matsucoccus spp., p. 64 



2. Galls on firs. 



a. Buds of grand fir badly swollen into "gouty" knobs 



Chermes piceae, p. 59 

 6. Leaf swellings or apical bud galls enclosing pink or 



red maggots Gall midges, p. 70 



3. Galls on spruce. 



a. Cone-shaped galls on terminal twigs Chermes, p. 58 



b. Apical bud gall enclosing pink or red maggots 



Gall midges, p. 70 



4. Galls on juniper, or cedar. 



a. Slightly enlarged fruit and conical bud galls 



Gall midges, p. 70 



b. Prickly, burrlike or conical galls on twigs — Gall midges, p. 70 



B. Galls formed on broadleaved trees inhabited by: 



Small, white, legless, apparently headless larvae. .Cynipid wasps, p. 69 



Small pink or red maggots Gall midges, p. 70 



Small bugs with cottony wax secretions Gall aphids, p. 58 



Microscopic eight-legged mites Gall mites, p. 68 



The pine bud mite (Phytoptus pini Nal.) (Eriophyidae) is a 

 very minute yellow blister or gall mite, which has been found 

 causing injury to needles of Monterey, ponderosa, Jeffrey, digger, 

 knobcone, and other pines in California and Oregon. It also is 

 reported as causing stem gall in Europe. It feeds within the basal 

 sheath of the needle cluster and causes a premature shedding of 

 the needles and a weakening of the tree. A 10-percent miscible-oil 

 spray has given fairly satisfactory control, but the removal of 

 badly infested pine may at times be necessary. Many other species 

 of eriophyid mites are found on both coniferous and broadleaved 

 forest trees. 



CYNIPID OR GALL WASPS 



One group of small, four-winged, usually somber-colored yellow 

 to brown or black, antlike wasps (Cynipidae) are responsible for 

 the formation of a great variety of galls on the different parts of 

 various forest trees, but particularly on the oaks. These galls may 

 be large, round, and shiny, like the common oak apples, or very 

 irregular in shape and spiny, or may consist of just a tiny swelling 

 on leaf, twig, or root. The larvae that inhabit these galls are white, 



