86 Psyche [August 



it is a rather common insect in central New York and is readily 

 distinguished from its relatives not only by its structure but by its 

 habits as well. Although Swaine {loc. cit.) mentions only hem- 

 lock (Tsuga canadensis Engelm) as the host tree, the writer has 

 never been able to find it in this tree, but has observed hundreds 

 of brood-burrows and thousands of specimens in all stages in the 

 inner bark of white pine. This is especially unusual when we 

 know that the type locality of this species is central New York 

 (Ithaca) and our observations were made in the same general 

 region of the state. 



Ips longidens in central New York may work either as a primary 

 or a secondary enemy of the white pine. It is found most com- 

 monly in the^ lower and middle regions of the trunks of trees in the 

 pole stage — i. e., from 4 to 8 inches in diameter. In larger trees, 

 where it sometimes occurs, its brood-burrows are constructed in 

 the middle and upper trunk regions and occasionally in the tops 

 and branches. It is thus evident that the factor which determines 

 the choice of location for breeding is the character of the bark. It 

 prefers bark upon the older sapling or pole stage of white pine, 

 the surface of which is roughened but which is still less than one 

 fourth of an inch in thickness, although in a few instances the brood 

 has been found successfully established in bark of a thickness as 

 great as one half of an inch. On the other hand, the beetles have 

 been induced to breed in captivity in limbs on which the bark is 

 less than one eighth of an inch thick and the surface of which is 

 smooth except near the origin of smaller limbs. 



The brood of Ips longidens was found nearly exclusively in white 

 pines of from 4 to 8 inches D. B. H. which were either dying or 

 had been more or less weakened by overshading. The tops of 

 these trees were small and ragged, the bark was thin, and the 

 foliage scanty. Usually at the time when the beetles enter the 

 trees the foliage has begun to turn yellow, but in some cases there 

 are no indications that the tree is actually dying, but only of a 

 weakened or suppressed condition. There can be no doubt that 

 in many cases these bark beetles are the actual cause of the death 

 of trees which would otherwise survive for may years. Ips longi- 

 dens will also breed in felled pines in the pole stage and in the tops 

 of larger trees. 



The brood-burrows are always started in the new host tree by 



