1919] Blackmail — Notes on Forest Insects 89 



simple cylindrical feeding burrows with no indication of a nuptial 

 chamber. On April 1, all of the beetles were still in their feeding 

 burrows, but by April 20, all but two or three had emerged and 

 males and females were in newly established brood-burrows. On 

 June 4, pupse and callow Adults of the new generation were ob- 

 tained from these burrows. It is thus seen that, under laboratory 

 conditions, callow adults of the new generation may be obtained 

 from mature beetles in about 50 days, but these are not sexually 

 mature until they have fed on the inner bark and sapwood for 

 several weeks or a month. It is apparent that in central New York 

 it is possible under field conditions for Ips longidens to complete 

 two generations in an average year and in an especially long, warm 

 season to increase this to two and one-half generations. Observa- 

 tions extending over a period of six years, however, convince the 

 writer that ordinarily a single generation is the rule, although a 

 partial second brood is by no means uncommon. There is thus 

 a decided mixing of generations and new brood-burrows may be 

 started at any time from May 15 (over-wintered adults) to Sep- 

 tember 15. Both adults and larvae have been taken in the field on 

 various dates including every month except December. The 

 larvae are as successful in withstanding winter conditions as are 

 the young fully colored adults, and much more successful than are 

 the callow beetles and pupae. 



The over-wintered adults leave their old hosts considerably 

 later than do some other bark beetles. An instance of this was 

 observed in the field by the writer in the spring of 1915. On April 

 24 of that year, the first individual of Pityogenes hopkinsi a male, 

 was observed to have emerged and started its nuptial chamber in 

 a new host near at hand. Within a week nearly all of the over- 

 wintered males and many of the females had left this old host. 

 On the other hand the over-wintered adults of Ips longidens, which 

 occurred in the trunk of the same tree, did not leave their old host 

 in any numbers until the middle and latter part of May. 



Ips longidens has been found associated in the same tree ; with a 

 considerable number of other bark and wood boring forms. Those 

 most commonly associated include Ips pini Say, Pityogenes hop- 

 kinsi Swaine, Crypturgns atomiis Lee, Graphisurus fasciatvs DeG., 

 and Monohammus scnfellatvs Say. These occur very commonly 

 in the same regions in which Ips longidens prefers to breed. Other 



