Field Studies of the Non-Social Wasps 385 
was found at the bottom of a 10-inch tunnel in a stem. 
The cell itself was % inch deep, and covered with a fine 
partition 4% inch thick; six inches above this was another 
partition just like the first; otherwise the channel was 
empty. The purpose of this additional partition re- 
mains a mystery; it may have been only a temporary 
structure put in to give added protection to the first cell 
until the time when the mother was ready to build 
additional cells. This cell contained prey, twelve fresh 
dead flies; five were of the species Agromyza virens 
Loew. [C. T. Greene], four of Phorbia fusciceps Zett. 
[C. T. Greene] and three Agromyza burgessi Malloch 
[C. T. Greene]. A very small larva was imbiling from 
one of the Phorbia flies. 
The observation of many nests like those described 
above seems to fully justify the conclusion that these 
wasps make an interesting distinction between partitions 
and the fillings for the large unused galleries above the 
top cell. The same pithy material, bitten out of the walls 
of the channel, is used for both, but for the use as plugs 
and partitions it is chewed up fine and made very com- 
pact, while for the purpose of filling it is just bitten out 
in coarse chips, and loosely dropped into place. Figure 
50 shows the two kinds of material. 
Of nine twigs taken during the winter of 1919-20, I 
found the number of cells for each twig to vary from 
4to9. To be exact: 
No. of Twigs Cells 
1 4 
3 5 
2 6 
1 7 
2 9 
