115 



until, in the older females, it may become as broad as the head of a 

 pin. 



It must not be inferred from the foreg-oiug- statements that the 

 scales of this group, similar as they are in appearance, are by any 

 means equally important to the nurseryman. The San Jose scale 



is one of the most destruc- 

 tive general fruit insects 

 known to entomology. The 

 Forbes scale is of minor 

 economic importance, oc- 

 casionally becoming injuri- 

 ous to here and there a fruit 

 tree, but under ordinary 

 circumstances scarcely de- 

 serving of serious notice. 

 The Putnam scale is not 

 a general fruit scale. It 

 has appeared in destructive 

 numbers on the currant, 

 but is found mainly on or- 

 namental trees such as the 

 ash, beech, hackberry, lin- 

 den, and maple. It has been 

 reported from the peach but 

 it is not known to be de- 

 structive to that fruit. The 

 walnut scale is of still less 

 Fig. 6. The Forhks Scale: <?, natural practical importance, occur- 

 size on cherry twig; /', female ring in nurseries in numbers 

 scale; r, male scale. ^q ^q injury, SO far as we 



have seen in Illinois, only on a few ornamental trees. It has 

 been elsewhere noticed, however, upon pear, cherry, apple, apricot 

 and plum, and may become generally destructive. 



A little close and careful observation and the recollection of 

 one or two peculiarities of habit will enable the fruit grower to 

 distinguish these four scales one from another in the majority 

 of cases, but for positive certainty in their recognition it is 

 necessary to refer specimens to an entomological expert. In the 

 Forbes scale the ring-and-nipple mark in the center is usually 

 snow-white or nearly so, while in the San Jose scale it is almost 

 always sooty black. The former, moreover, rarely becomes so 

 abundant on the tree as the San Jose s cale usually does. It is 

 commonest perhaps on the cherry, and hence has been sometimes 



