Field Studies of the Non-Social Wasps 443 
CHAPTER VII. 
Tue Nestine Hasrrs or tor YELLOW-Leccep Mup- 
Daupsr, Sceliphron caementarium., 
What insect can be mentioned which is so universally 
known as the common yellow-legged mud-dauber? It 
occurs in almost all parts of this country; almost every 
school-child recognizes it as a frequenter of the mud- 
puddles and every farmer and housewife is familiar with 
the mud nests plastered on the ceilings of porches, barns 
or even attics. One would naturally conclude that the 
last word had been said upon the life-history of so com- 
mon a creature; perhaps this simple assumption has 
been one reason for the neglect of it by investigators; 
at any rate, this astonishing condition exists, that the 
literature contains less information regarding this near 
neighbor of ours than it has concerning many far-away 
and obscure species. To be sure, the Peckhams have 
given a very interesting account, but since they placed 
the two species most common in their neighborhood in 
the same genus, under the names Pelopoeus cementarius 
and P. caeruleus, and throughout the fifteen pages of 
their account of habits they make no distinction in the 
way of attributing certain habits to one wasp or the 
other, one cannot tell which species they mean. The 
confusion is more apparent when one runs across sen- 
tences such as this: ‘‘Almost invariably she decides to 
build for herself, although now and then she uses an 
old nest,’’ or ‘‘in favorable weather the blue wasp often 
builds and stores a nest in a single day.’’ It is easy 
and natural, when one sees them store and seal a cell, 
to conclude that of course they made it. While one is 
very reticent about questioning the statements of such 
observers as the Peckhams, I must state that in my own 
