446 Trans. Acad. Sci. of St. Louis 
stands on her head the better to bite out a chunk of mud 
to carry to her nest, while the blue wasp, gently coming 
to the water’s very edge, takes long draughts and de- 
parts, but avoids the mud. Now I find that the latter 
species is a carrier of water by the aid of which she 
breaks into the nest of the former species. 
The next item of discussion, the position in the cell 
of the spider upon which the egg has been laid, deserves 
the full quotation: ‘‘Our wasps did not share the habit 
of those observed in France in laying the egg on the 
first spider placed in the cell. Indeed, we found that it 
was only after the nest was completely provisioned that 
the egg was laid on the abdomen of one of the last 
brought in. The importance which Fabre attaches to 
the early laying of the egg seems to us a little exagger- 
ated, as the difference in time, in the two methods of 
procedure, cannot be enough to give much advantage 
either way.’’ As for our American wasps, the Peck- 
hams are both right and wrong, for S. caementariwm, 
like Fabre’s wasps, always deposit the egg on the first 
spider brought into the cell, and C. caerulewm always 
lays the egg on the last one. 
This distinction seems absurdly insignificant now, but 
wait. When large numbers of nests are studied in the lab- 
oratory, only a few can be found which are in condition to 
throw light on this subject. Usually one finds, upon break- 
ing open the nests, that the young are either grown larve@ 
or pup, so one cannot tell just what the position of the 
egg was, but a few are found with the egg or small 
larva at one end of the cell to indicate where it was 
born. Within this selected lot of material it is then 
necessary to determine which is the back and which the 
front of the cell—a matter which is not so simple as it 
might appear when the nest is sealed and well daubed 
