1928] The Nesting Habits of the Pulp-Making Bee 103 
emergence was that in a nest found in a sumac twig in Decem- 
ber, 1918. The stalk contained a hollow six inches in depth, at 
the very bottom of which were four cells, close together. The top 
was hollow for three inches, except that the orifice was plugged 
for an inch with che wed-up vegetable material. The twig was 
kept indoors, and on March 13 two adults emerged. These 
were the two nearest to the top. Quite unintentionally I aided 
these two in escaping from their cells, by splitting open the stem 
for inspection; they emerged by merely biting their way through 
the side of their cocoons, and escaped. Fully developed young 
adults could be seen through the transparent walls of the 
other two cocoons. Mica was sealed over the missing wall to the 
very top of the stem to compel these remaining bees to attempt 
to get out by crawling upward by their natural route. 
On March 26th I found that the third consecutive bee had 
emerged from its cocoon. Early next morning it was busy biting 
its way upward; it entirely demolished the empty cocoon of no. 
2 in its upward course and kicked the fragments back in a heap 
at the bottom. It then had its head against the partitioning 
plug, where it faced a harder task at breaking through. 
The next morning, the beginning of the third day, this bee, while 
apparently in the same position, was industriously attacking 
this roof, the one which the elder sister, no. 2, should normally 
have cleared away for it. Its own cell was clean; all debris had 
been kicked to the bottom. It was attacking not only the roof 
or partition, but also the surrounding pith against which it 
was built; it had already bitten out enough of the pith on the 
sides to enlarge the original cell considerably. It must be re- 
membered that no. 3 was doing additional work. Had nos. 1 
and 2 emerged normally, each biting the roof out of its own cell, 
she would not have had this additional work to do, since each 
bee has only to break through the roof of its own cell to reach 
liberty. Unlike certain wasps, e. g. Trypoxylon politum , which 
can instinctively remove but one covering, and, even if they have 
the ability to go through a second wall, would rather die than 
make the attempt, this bee had already shown that she could 
suit her action to the needs, and not do so by mere instinct, 
