19 



EXPLANATION OF DIAGRAM. 



The accompanying di- 

 agram (fig. 1) illustrates 

 the dormant and active 

 periods and the rate of 

 development of Den- 

 droctonus piceaperda. 

 The symbols at the left 

 represent the different 

 stages of the insect in 

 the bark of infested 

 trees when activity 

 ceases, about the mid- 

 dle of October: (•) rep- 

 resents the mature, im- 

 mature, and very young 

 adults; (0) represents 

 the pupae; (° o O) rep- 

 resent three stages of the 

 larvae, and ( • ) the eggs. 



Commencing with the 

 mature adults, in the 

 upper line, the normal, 

 or average, dormant and 

 active periods, and the 

 periods of development 

 are represented as fol- 

 lows: The dormant pe- 

 riod of two hundred and 

 thirty-two days ends 

 about the 5th of June; 

 in about ten days more 

 the adults commence to 

 emerge; in twenty days 

 eggs are deposited; in 

 thirty days larvae com- 

 mence to appear ; in sixty 

 days the larvae are ma- 

 tured ; in sixty-five days 

 pupa? commence to de- 

 velop; and in eighty 

 days from the time ac- 

 tivity commences the 

 first adults develop; 

 they probably continue 







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