2 
injurious to both girdled and felled trees. One species of this latter class 
causes more damage, perhaps, than all of the many other insects which 
have been found boring in the wood of girdled trees. It is known tech- 
nically as Platypus compositus Say, and may be distinguished from 
other cypress pin-borers by the English name “ girdled-cypress pin- 
borer,’’ or Pan American Platypus. (See fig. 1.) 
The facts and evidence of immediate practical importance may be 
briefly stated as follows: Trees girdled in March, April, October, and 
November were not at all or but slightly damaged by the girdled-cypress 
pin-borer, while those girdled in May, June, July, and September were 
more or less seriously damaged. There were indications that trees 
girdled in August were not damaged as badly as those girdled in July 
Fria. 1.—Work of ambrosia beetles in oak: a, Monarthrum mali and work; b, Platypus compositus 
and work; ¢c, bark; d, sapwood; e, heartwood; f, character of work in lumber from injured 
log. (Author’s illustration.) 
and September; also, that trees girdled from December to February 
were not seriously affected. It was found that local factors and con- 
ditions had an important bearing on whether or not injury resulted from 
girdling at given dates. In some localities there was practically no 
injury to trees girdled on any of the dates. In other localities some of 
the trees girdled on a given date would be badly damaged while others 
would show no trace of injuries. The absence of injuries in the former 
localities may have been due to the presence of a limited number of the 
insects, or to their being attracted to felled trees in preference to the 
standing girdled ones, or to some other unknown causes. The attack 
on individual trees is evidently due to individual differences in the trees 
themselves, for our general observations indicate quite clearly that 
certain types and varieties of trees of the same species are more resistant 
