384 Trans. Acad. Sci. of St. Louts 
packed type, and for 2 inches above that it was the coarse, 
rough-hewn kind, loosely packed. The gallery for a 
short distance above this was the mine from which the 
material had come; the walls there had been scraped 
clean of the pith, clear down to the wood. Above this 
the mine suddenly narrowed into the normal passage a 
little more than 1/16 inch wide. In fact, all the way down 
the sides of this long fill, the pith on the walls had been 
all dug out. Apparently the insect works at the mining 
operation from the bottom upward; when she has need 
of a plug over the top cell she pulverizes and compresses 
this material into a plug of desired thickness, about %4 
inch, and above this she tears the pith from the walls in 
coarse bits as she works upward and drops the stuff 
below. In this case she finally ceased when she had made 
this coarse portion of the plug 2 inches deep, but left 
the mine unfilled. Had she been guided by blind instinct 
only, she would have continued this work to the end, 
tearing down above and packing below, until she reached 
the top. Instead of that, this wasp went part way up 
the narrow passageway and resumed biting the pith from 
the walls and packing the large pieces into a partition 
and continued until she had a plug %4-inch thick and 
a comparable mine just above it. The small remainder 
of the passage was open. 
Other communities of H. stirpicolus which emerged 
from elder stems displayed other variations in their 
method of handling pith for plugs and for filling in the 
top. Some of the material was coarse, some fine, though 
the condition seemed usually to meet the need. Some- 
times the top of the channel was filled and sometimes 
left open. It seems there was no hard and fast rule to be 
followed, but individual temperament and the needs of 
the site were the deciding factors. One newly filled cell 
