Field Studies of the Non-Social Wasps 361 
out garnishments, according to whether the nest is in 
the open or in protected situations. All of these species 
carry mud from afar to build their nests. Sometimes, 
however, some individuals of P. mellipes eliminate this 
work by building their nests in a daub of dry mud and 
carrying only the water to this point of operations, thus 
Saving a great amount of the work. Not all individ- 
uals of P. mellipes behave in this manner; this variation 
shows at least that this habit is new to the species and 
probably in an incipient stage of higher development. 
One must not overlook, too, that Hartman has discov- 
ered that Agenia subcorticalis uses the cells of Pelopoeus 
merely as cavities in which to build her own small cells 
of the ancestral type. Thus she may have as many as 
five of her own cells inside a single chamber of a mud- 
dauber’s nest. Indeed, A. subcorticalis too goes a step 
farther and not only closes each of her individual cells, 
but builds a plug over the opening to the large chamber, 
thus offering to her enemies an additional rampart. 
The dirt is taken from the very nest in which she is 
building her own; she gnaws off pellets, after having 
moistened the dirt with water from her gullet. 
When one sees the variations in nesting habits within 
each of these two species, A. Mellipes and A. subcorti- 
calis, and compares the behavior of the various species 
within the genus, one cannot help but look toward the 
day when naturalists will be able to show the graduated 
Series from the nest of most primitive structure to one 
of great complexity and the relationship between the 
nesting habits and anatomical characteristics. 
