112 



away. They spread from dead and decaying- wood to the living- 

 roots of trees, and may thus continue indefinitely in the g-round. 

 Soil on which trees atfected by this disease have grown 

 should of course be abandoned for nursery' or orchard purposes, 

 and old forest land should be avoided for the g-rowth of nursery 

 stock until it has been cultivated long enoug-h in some other 

 crop to insure the practical disappearance of rotten wood and of 

 fung-i g-rowing- therefrom. No treatment of this disease can be 

 expected to serve any useful purpose in the nursery, but an affected 

 tree should be at once destroyed as valueless. 



The Scale Insects. 

 {Corr/(f(r.) 



The scale insects, or bark-lice, are on the whole much the 

 most important nursery insects from our point of view; the most 

 likely, that is, to infest the nursery in a way and at a time to make 

 it probable that they will be conveyed on nurserj* stock to its pur- 

 chaser. All here treated are capable of noteworthy injury to 

 young- trees, and one, the notorious San Jose Scale, is the most 

 dang-erous and destructive insect pest of the nursery. Most of them 

 have an outward appearance so little like that of other insects 

 that one not correctly informed in advance would never surmise 

 that they were insects at all, but there is nevertheless a family 

 resemblance among them such that one to whom the peculiarities 

 of two or three prominent kinds have been pointed out will usually 

 recognize most others. A few, however, are so small and other- 

 wise inconspicuous that they are very little likely to be detected 

 by the ordinary observer unless they become so abundant as to pro- 

 duce a notable effect on the health of the infested tree. 



The greater part of them are nearly or quite motionless when 

 full grown, remaining fixed to the bark, or in some cases to the 

 leaf, like inanimate objects, most of them completely concealed be- 

 neath a delicate scale, a waxy secretion from the insect's surface. 

 For a short time after birth they have considerable power of active 

 locomotion, of which they make use to distribute themselves over 

 the surface of the plant and to find a suitable point of attachment. 

 Having selected this, their long- and threadlike beaks are pushed 

 deep into the living tissue of the tree, from which they proceed to 

 suck the sap. 



The greater part of them hatch from eggs laid by the female 

 under the scale which conceals her body, and remain there, under 

 its protection, after the parent has died and dried away. In a few 



