392 Trans. Acad. Sei. of St. Louris 
cleaning out the cell it takes double work to carry out 
the rubbish and bring in new material; hence they have 
combined the two activities into one of actual utility. 
Here again is seen the process of learning, or, if one pre- 
fers to say it otherwise, the profiting from experience 
erystallized into frequent or customary action. In this 
nest also the vestiges of a cocoon varied; some had a com- 
plete head-piece, while others had only a thin dribble of 
cocooning substance varnished against the walls. 
On ‘April 12 they were still in the form of three per- 
fect pupae; by May 1 they were fully pigmented, and on 
May 12 they emerged. The mica, which served as a trans- 
parent wall, was not securely sealed to the split twig, 
and they escaped from their cells sidewise without break- 
ing the plugs, so I could not ascertain their normal mode 
of emergence. 
Still another twig was opened on March 30, which con- 
tained four quiet larvae. This hollow twig also showed 
clearly that other wasps had been here to nest in days 
gone by, and had left numerous partitions with holes 
bored in their centers. This mother had not taken the 
trouble to clear out this debris, but had made cells above 
and below these ruins. In this large, hollow sumac twig 
was a floor of mud, placed 4% inches below the top; 4 
cell 5g inch in length built on top of this floor had one 
larva. The 114 inch above that was empty, but con- 
tained the two old rings of mud, remains of previous 
cells; with little effort the new mother could have torn 
them away and made two cells for her young. This she 
did not do; hence I, prying into her home affairs long 
after, denounce her as a poor domestic manager. The 
four cells above this, each approximately % inch im 
length, contained four good larvae. The final plug was 
an inch from the top, and unlike the other series of cells, 
