Field Studies of the Non-Social Wasps 375 
below the other, excepting the lower two, where the pith 
chamber was wide enough to harbor them two abreast. 
THe Desris-Carryine Wasp, Silaon niger Roh. 
[S. ‘A. Rohwer]. 
After opening a number of Silaon niger nests in sumac 
twigs, I soon became so familiar with their characteristics 
that I could easily recognize them at sight. After they 
had grown to seem such common and familiar objects, it 
was indeed a shock when I discovered that the previous 
records in the literature contain nothing about this quaint 
little home built of rubbish or even the fact that 9. niger 
(fig. 48) nests in twigs. 
For a long time, in lieu of a familiar name I called 
it the debris-carrying wasp. It nests in hollow twigs, 
but the evidence indicates that it uses old burrows left 
by other insects, and so probably does not do any ex- 
cavating of its own. Some of the nests have contained 
relics of the former occupants packed in the bottom of 
the burrow (see pith chips left by Hypocrabro stirpicolus 
at [x] in fig. 49); others had at the aperture at the top 
traces of the mud seal of the former Eumenid, and one 
Showed that a Ceratina bee had formerly nested there. 
S. niger does not make either partitions or cells in 
this burrow, but merely fills up the tunnel from bottom 
to top with bits of any material that she finds conven- 
lent, with her eggs and provisions scattered along at 
intervals in the mass. It is an unsolved mystery how 
the tender larva can survive unprotected in this heter- 
ogenous mixture, or how it can find all of its food. I 
have never been so fortunate as to find a nest with the 
young in the early stages of development, and from its 
table it leaves not a crumb, that one might know what 
its food was. Figure 49 shows three firm little clay- 
