344 Trans. Acad. Sci. of St. Louis 
The stability of these two habits, in groups of or- 
ganisms separated from each other by half the girth of 
the earth, lends a tinge of romance to the subject. Shall 
we say that these habits are instinctive and of so strong 
a type that they persist regardless of time and space, 
or shall we rather say that these groups of insects, m 
the two remote regions, have independently acquired the 
same habits, through the similarity of their problems or 
through the similarity of their environment? 
I said that in the evolution of nest-building activities, 
P. mellipes is in advance of any other member of the 
Pseudagenia clan, despite the fact that the Philippine 
Pseudagenia are likewise water-carriers and likewise use 
the abdomen as a tool wherewith to fashion the nest. The 
facts are that the oriental wasps still carry the building 
material to the site, while some individuals of our P. 
mellipes have advanced to the point where the carrying 
proclivities are eliminated. Not all of our P. mellipes 
have abandoned their habit of carrying clay, for we have 
formerly recorded three and four-celled nests taken from 
under loose pieces of bark (fig. 40), and a four-celled nest 
that was found in an oak-apple still hanging on the tree. 
All of these nests in due season gave forth P. mellipes, 
and both situations certainly entailed the carrying of mud 
from a distance. Other nests which must have involved 
the new method of building, have been found in old nests 
of the pipe-organ wasp, Trypowylon politum (fig. 63), 
and in the abandoned nests of Sceliphron caementarium 
(fig. 38), where these wasps had built their little cells 
within the larger ones of both species. Thus we see the 
most recent accomplishment of the species, that of carTy- 
ing water, to be so new as not to have permeated the race, 
and the pioneers in this habit are the wasps observed at 
an obscure corner of the earth called Wickes. 
