14 SCALE INSECTS. 



scale is elongate; the female scale is circular. Eighteen 

 days after birth the male scale enters the puptie stage, and 

 about six days later backs out from under the scale as a 

 delicate two-winged, fly-like insect with long feelers and 

 six legs, another set having replaced the one lost. It is 

 orange in color. Thirty days from birth the females are 

 full-grown, and from three to seven days later begin to pro- 

 duce young, making in all about 40 days as the period re- 

 quired for bringing a generation to maturity. 



One of the questions most frequently asked the writer 

 is concerning number of eggs or young brought forth by 

 a single female. A series of experiments was performed 

 by the department at Washington, in which one over- 

 wintered female was placed upon each of seven trees, and 

 when their offspring were mature all were removed save 

 one fertilized female on each tree, and the same process 

 repeated until the cold weather closed the breeding season. 

 From accurate observations upon these experiments, it was 

 estimated that if all the young of one over- wintered female 

 lived, the increase from this one and her i^rogeny for the 

 one season would be 3,21(),0S0,400. These would be the 

 descendants from a single insect in a single season, if all 

 fulfilled their functions in life. While it is hardly to be 

 expected that all should live, yet, granting that a goodly 

 number should perish prematurely, even then it is readily 

 seen that enough survive to explain the sudden destruc- 

 tion of trees attacked. As before stated, the reproducing 

 period of the adult female is about six weeks. Nine to 

 ten young are brought forth every 24 hours, making a 

 total production of about 400 individuals from one insect. 

 The fact that all are not born at the same time is another 

 point in their favor and against easy means of destruction. 

 Many of the older washes used are effective only ujjon the 

 active larva; hence it is readily perceived that applications 

 of such washes to be successful should be applied almost 

 dailv. 



