402 



WEST VIRGINIA EXPERIMENT STATION. 



Fig. L.XX "Diagram showing delopment and generations from hibernating series of 

 Dendroctonus frontalis. 



near Morgantown in April, and the first eggs are deposited 

 about the 20th. The hibernating pupae, larvae, and eggs con- 

 tinue to yield adults until about the 20th of June; by which 

 time adults of the first series of broods commence to emerge, 

 and continue emerging until about the 18th of August. By 

 this time adults of the second series of broods commence to 

 emerge and continue to come out until about the 18th of Octo- 

 ber, when adults of the third brood commence to appear. The 

 adults of this series deposit eggs for the hibernating broods, 

 eggs and nearly matured larvae of which pass the winter in the 

 brood galleries and larval mines in the inner bark ; so that 

 there is, under average conditions, three broods each year. 1 



The foregoing diagram, based upon an average of sixty days 

 from the egg to the emerging of the adult, will illustrate 

 the number of broods or generations from the hibernating eggs 

 to adults, which may developein a single season. Those de- 

 veloping from the first eggs deposited by the hibernating adult 

 females are shown in line 1, from hibernating pupa and matur- 

 ed larvae, in lines 2 and 3; from nearly matured to very young 

 larvae, in lines 4, 5 and 6; and from eggs, in line 7, Thus the 

 hibernating individuals may represent seven series, each separ- 

 ated by a period of ten days. The 1st to 4th developing 

 three generations each between April 20th and November 16th 

 and the 5th to 7th developing two generations each between 



1. This has reference to the Upper Austral area In West Virginia. There is probably 

 not over two broods in the Transition and possibly not over one in the Canadian; and 

 under the most favorable conditions it is possible for more than three broods to de- 

 velop at low altitudes audin the southern part of the State. 



