Field Studies of the Non-Social Wasps 369 
CHAPTER IV. 
Aw AssoRTMENT oF Twic-DweE.Luine Wasps. 
Tue Apuip-Huntress, Diphlebus biparitor Fox 
(S. A. Rohwer). 
' This wasp (fig. 46) is highly interesting because it is, 
so far as I know, unique in its manner of nest-building. 
Twig-inhabiting wasps generally excavate a tunnel in the 
pith, or find one already excavated, then build partitions 
across this hollow, dividing it into rooms, and fill each 
with food and deposit an egg. Thus these cells are 
completed one atop the other. This wasp, however, digs 
out a narrow tunnel down one side of the pith of a 
fairly wide stalk, or digs one which fluctuates from side 
to side in the pith chamber, and then adds pockets 
branching off to the side of this, in which the nest pro- 
visions and egg are placed. This necessarily means that 
thick stems must be used, for in narrow twigs this type 
of nest would be impossible. A more complete idea of 
the nest of this species will be gained from the descrip- 
tion of three or four which I studied in detail. Indi- 
vidual variations are always of great interest and value, 
but I have not yet observed a sufficient number of these 
nests to know which is the standard form for the species 
and which the individual digression in certain details, 
so I shall record them here in the hope of learning more 
later. 
The first nest discovered was in the pith of a large 
sumac twig. The tunnel was about 3/16 inch in diam- 
eter. Careful cutting revealed the fact that this burrow 
went down one side through the soft pith very near to 
the wall, and there were several little pockets branching 
off from this at intervals, extending across this substance 
