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fall survives the winter to resume in spring-, even though she 

 hring forth but a single }'oung; and no }-()ung that set after 

 the sap ceases to circulate in the tree ever reacli reproductive 

 condition. Only those that set in early to middle October — 

 perhai)S late September here — resume growth in spring. The 

 males issue early in June and by the middle of that month 

 every female is in the larva business. 



Each sucking insect extracts from the tree a tiny droplet 

 of sap, and the thousands that infest it mean a perceptible 

 drain on the vitality of the plant. But that is not all : at every 

 feeding point there is also introduced a tiny droplet of saliva 

 which may cause a purplish discoloration and. does cause inter- 

 ference with the functions of the plant cell, so that a badly 

 infested tree which has maintained a good showing throughout 

 the season often finds itself unable to start again in spring; and 

 then the fruit grower is likely to blame the insecticide for the 

 condition. Occasionally a tree even starts from the stored 

 material in the buds, and when that is exhausted it wilts and 

 dies, simply because the poisoned bast cells will not carry the 

 sap. 



The minute size of the insect enables it, in the larval stage, 

 to get under leaf and bud scales ; in the plant vestiture and 

 under any sort of loose scales of bark on the trunk, branches or 

 the extreme tip of the tree. 



Now here is our problem. We must apply to a tree that 

 may be 20 feet high and 30 feet in diameter some material 

 that will reach and kill every insect on that tree, for if we 

 leave even one pair, next fall may give us 1,000,000,000 as 

 their descendants; and you will see at once that our problem 

 divides into two parts — the material that kills, which it is the 

 entomologist's business to provide, and the mechanical task of 

 ap])hing it, which is none of his business, strictly speaking, but 

 which has been saddled upon him by force of circumstances. 



Let us consider hrst the insecticide matter. There is only 

 one period in the life of the insect when it is not protected by a 

 scaly co\'ering — the day or two just after birth, wdiile it is 

 crawling al)out looking for a place to set. This stage is during 

 the period when the trees are full of foliage and when the 

 mechanical task of reaching every twig and branch is well 



