12 College of Forestry 
once at Syracuse (pine), infested wood known to contain 
full-grown grubs was barked and one year later still con- 
tained living larve or young adults. The barking of the 
wood created an unusual condition in several respects, but 
especially it rendered the wood more subject to dessication, 
and this abnormal dryness was doubtless the factor which 
retarded the development of the larve. It is interesting that 
the larve and young adults under these conditions were 
apparently normal in all respects except as regards time of 
emergence. 
As the larva continues to grow the “ retiring burrow ” in 
the sapwood is enlarged from time to time to accommodate 
its larger bulk, and when the larva reaches full growth this 
is carried deeper into the limb or trunk to form the pupation 
chamber. This, in burrows in the trunk, may he in the 
heartwood several inches from the bark. Always before 
pupation a passageway, circular in section, is extended out-- 
ward toward the bark, usually ending a fraction of an inch 
from the inner bark. This is to act as an exit for the adult 
when it emerges. The larval entrance to the pupal chamber 
is then plugged with excelsior like frass and the larva pupates 
in the deeper part of the burrow. The emergence hole 
through the bark is nearly exactly circular in outline and 
from 4.6 to 6.5 mm. in diameter (Fig. 16). 
Eccoptogaster picee and Polygraphus rufipennis precede 
M. scutellatus in larch and Serropalpus barbatus was bred 
from it the same season.* In balsam it is most often asso- 
ciated with Pitogenes punctipennis Lee. and with Urocerus 
albicornis. In pine M. scutellatus is often associated in the 
limbs with the sister species M. titillator, Ips pini Say, Pito- 
genes hopkinsi Swaine, and others, and in the trunks with 
M. titillator, M. confusor, Ips longidens Swaine, Graphi- 
surus faciatus De G., Rhagium lineatum Oliv., Pytho ameri- 
canus Warby, ete. 
‘ 
* In Tree IX it was associated with Polygraphus rufipennis, Neoclytus 
longipes and Xylotrchus undulatus. 
