Field Studies of the Non-Social Wasps 445 
the outside of the sealed nest, forming a conspicuous 
but fragile decoration (fig. 67), instead of the more cus- 
tomary method of spreading the last loads of mud over 
the outside of the nest, thus making an excellent rein- 
forcement for the finished nest. Since this occurs so 
infrequently (in my count about one in every twenty 
or so were decorated), I suspected that this was done 
by Chalybion and not by Sceliphron, although from the 
Peckhams’ account it would seem that in both species 
some mothers are so artistically endowed. The ma- 
jority of these decorated nests were Sceliphron, and in 
the few cases where they proved to be Chalybion the 
usual evidence was present to indicate that the cells 
had been gnawed open and replugged, and hence were 
being used for the second time. So we may safely con- 
clude that the decorations are put on by Sceliphron and 
that these nests may later be used by Chalybion the same 
as other nests. 
The same authors state that they found 546 nests out 
of 573 with the openings on top, with the longitudinal 
axis nearly vertical, while only 27 were built in a hori- 
zontal position with the opening at the side. While 1 
have not actually counted the nests in these two posi- 
tions, I do find that in the St. Louis region the opposite 
. occurs. This, however, and the cause thereof, will bear 
further investigation. 
The direct statement, ‘‘In favorable weather the wasp 
often builds and stores a nest in a single day,’’ is abso- 
lutely contrary to anything I have seen in nest-building 
by C. caerulewm. In fact, this point first led me to sus- 
pect that C. caeruleum follows parasitic habits. For 
years I have seen both species at mud-puddles; there 
S. caementarium buries her head deep in the soft mud 
a few inches from the water’s edge and often even 
