390 Trans. Acad. Sci. of St. Louis 
tions suffer a shock. We must excuse O. conformis, but 
logic seems to have been omitted from her course of train- 
ing, which has been entirely practical. There must surely 
be something inherent in the organism to give rise to the 
exact opposite from the normal sequence, since surely 
nothing in the temperature or environment, which is com- 
mon to all in the nest, could reverse the order of their 
development. In the first nest examined we see the 
changes going on in the five individuals to be in continu- 
ous order, from the simple constriction of the larva 
preparatory to changing, to the completely formed 
mummy with pigmented eyes, and all of this in the order 
exactly opposite to their actual ages. The completed 
pupa, at the time of examination, was at the top, despite 
the fact that its egg had been the last deposited. Down 
the line the organisms were less and less developed, until 
in the bottom cell wag the first-born just a little better 
than a larva. 
A second Odynerus nest was found snug within an 
elder twig in Tower Grove Park on February 13, 1920. 
On March 31 it was found that the three pupae in the 
three cells were all fully developed, but by the degree of 
pigmentation of the eyes it was evident that this family, 
too, was in all readiness for emergence inversely to the 
length of time each insect had spent in development, just 
as in the previous twig. 
The previous occupant of this twig (for all evidence 
was there that this family was not the first therein 
housed) had tunneled down only 214 inches. The mother 
of the present brood had not gone beyond this, but had 
put the mud floor for her first cell 14 inch above this ter- 
minus. The cells were rather small, only 36, 5/16 and 
9/16 inch in length, and the pupae seemed crowded; I 
expected that these would prove to be either males oF 
