INSECT ENEMIES OF WESTERN FORESTS 55 



to the leaves at the tips of branches, but during epidemics the 

 older needles on the branches are also fed upon, and large forest 

 areas may be completely defoliated and the trees killed. This group 

 of bud moths, while it includes hundreds of species of only minor 

 importance, also includes such conspicuous forest-tree defoliators 

 as the spruce budworm, blackheaded budworm, and lodgepole pine 

 needle tier. 



SAP-SUCKING INSECTS 



A large group of bugs, aphids, and scales belonging to the order 

 Hemiptera, and the mites of the class Arachnida, closely related 

 to insects, are equipped with slender beaks, which they insert into 

 the tender leaves or shoots of plants and feed by sucking the 

 juices from these succulent parts. These insects and mites are 

 more important in the orchard and garden, or to shade trees, 

 than they are in the forest. A few species, however, do noteworthy 

 damage to small forest trees, and a few are important enemies of 

 larger trees. 



On shade and ornamental trees sucking insects can be controlled 

 through the use of such contact sprays as lime-sulfur, miscible 

 oils, or nicotine sulfate mixed with soap solution. Under forest 

 conditions, however, the use of such sprays seldom is practicable, 

 and so far no control work of this kind has been undertaken in 

 western forests. 



Key to Diagnosis of Sap-Sucking Insect Injury 



A. Trees appearing sickly, leaves or stems not chewed but yellowing 

 or covered with small incrustations, scales, powdery or cottony 

 tufts, or small, soft-bodied insects. Trees frequently dripping 

 with sticky exudation or covered with black smut. 



1. Trees dripping with sticky exudation, black smut usually 



abundant. 



(a) Colonies of small, soft-bodied, pear-shaped, or 



globular bugs, usually with two cornicles or 

 protuberances on rear of abdomen, appearing 

 on leaves or tender stems Aphids, p. 56 



(b) Small circular, oval or elongated shells or scales 



on leaves or twigs Scales, p. 62 



2. Trees with white encrustations of cottony wax on leaves, 



twig or bark. Black smut often abundant 



Chermes or scales, pp. 58, 62 



3. Leaves sickly or yellowing in spots; little or no sticky 



exudation or black smut present. 



(a) Small tufts of cottony wax on under sides of 



leaves or stems Chermes or scales, pp. 58, 62 



(b) Small, globular, dark-brown or black insects 



hidden in crevices of bark, in needle fascicles, 



or on needles Matsucoccus spp., p. 64 



(c) Globules of spittle on stems or needles . . Spittlebugs, p. 66 



(d) Leaves covered with fine, nearly invisible webs or 



silvery coating Spider mites, p. 67 



B. Trees appearing in fairly good health but leaves or stems badly 

 stunted, galled, or swollen; sometimes with queer protuberances. 



1. Cone-shaped galls on terminal twigs of spruce. . .Chermes, p. 58 



2. Swollen twigs or galled bark covered with white incrusta- 



tions Cheques and Pinens, pp. 58, 61 



3. Galls at base of pine needles causing premature shedding 



Pine bud mite, p. 69 



