INSECT ENEMIES OF WESTERN FORESTS 49 



contain only one or two young in each chamber, and when the in- 

 sects emerge the galls flare open, and the scales drop from the twigs. 



The alternate form attacks western white pine and is easily recog- 

 nized by the waxy secretion that appears as a whitish-gray mold on 

 the bark and needles. The attacked foliage is apt to be sparse and 

 stunted; the needles fall prematurely, and the fascicles or bundle 

 sheaths are left protruding from the limbs as short spurs. The dam- 

 age is most frequently found on young white pines. In the last few 

 years it has become a rather important enemy of white pine seedlings 

 in eastern Washington, Idaho, and western Montana. The adults 

 appear as little hemispherical, brown scales one-sixteenth of an inch 

 in diameter, with a fringe of white hairs. The head and thorax are 

 completely covered by this shield. The life history has not been 

 thoroughly worked out, but is supposed to be as follows: Eggs are 

 laid for the new generation early in the summer. These soon hatch 

 and the young bark lice start sucking the juice from the white pine 

 twigs. Part of these insects develop wings and fly to the spruce, 

 Avhere they construct the terminal cone-shaped galls. The others 

 grow and reach the adult stage by the following spring. 



Pineus hoycei Annand makes similar galls on Engelmann spruce in 

 Oregon and Montana. The needles with enlarged bases are pressed 

 closely against the twigs and form intercommunicating chambers in 

 which about 15 nymphs are found. The alternate host is not known. 



Pineus horneri Annand feeds on the needles and twigs of Monterey 

 pine in California. 



Pineus coloradensis Gill, causes dense mats of dirty wax, covered 

 with mold, to form on the twigs of various pines, including ponderosa 

 pine, lodgepole pine, pinon, wdiite pine, sugar pine, and single leaf 

 piiion. It is found in Washington, Oregon, California, and Colorado. 



Pineus similis Gill, is found forming cone-shaped galls on blue 

 spruce and Engelmann spruce in Colorado, Oregon, and British 

 Columbia. The galls are shorter and thicker than those of Adelges 

 cooleyi^ and the chambers are intercommunicating. An alternate host 

 is not known. 



SCALE INSECTS 



(Coccidae) 



Scale insects form one of the most abundant and variable groups 

 of sap-sucking plant enemies. The young are mobile, small, and 

 inconspicuous, but unlike most other insects, after they have become 

 attached to a plant they lose all power of locomotion. They develop 

 a hard epidermis, a thick waxy covering, or a round or oblong shell, 

 and remain fixed in one position until they die. It is the female that 

 causes all of the injury to plants. The adult males often have wings, 

 eyes, antennae, and legs, but no mouth parts and so cannot take food. 

 They live only for a short time and are rarely seen. A large number 

 of species of scale insects infest nearly all forms of plant life, but 

 only a few of those that feed on forest trees are of major importance. 



Scale infestations on conifers, particularly those of the pine leaf 

 and California pine scales, are often associated with conditions where 

 dust and smoke occurs regularly in the atmosphere. Heavy scale 

 attacks on ponderosa pine trees bordering dusty roads have been 

 frequently observed as well as on trees exposed to air currents which 



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