Field Studies of the Non-Social Wasps 401 
either by the larva or by the mother. Certain of the 
Eumenidae, of which the genus Odynerus is one, make 
no cocoon, or at least a very poor one, before pupating. 
But here in this species we have a twig dweller that uses 
mud in an entirely new way, in that the mother supplies 
the dirt, and the larva somehow manipulates it into a 
cocoon. 
In 1917 one elder or sumac stalk, in 1919 three stems, 
and in the winter of 1921-22, two twigs were taken at 
Wickes, all of which harbored this species. The tunnels 
in these twigs had undoubtedly been dug out by the 
mother Odynerus; in this respect her work is very un- 
like that of certain other species of the genus, which 
habitually use old abandoned tunnels. She is unlike her 
sister species, too, in her method of using her mud. It 
will be r bered that others, such as O. foraminatus, 
etc., bring in wet mud and make partitions of circular 
dises, two of which (one at either end) make one room; 
since thesé rooms or cells are close together, end to end, 
their end walls are almost in juxtaposition, and really 
form a partition of two thin walls between the cells. 
When we examine the nests of this species we find the 
partitions made of pith, and between these partitions is 
& mud cocoon and an empty space (see fig. 52). Now 
these cocoons of mud are very puzzling, since it seems 
they can be made only by the larvae, and the mud must be 
supplied by the mother, since obviously the larvae can- 
not fare forth to gather mud. One might find a different 
explanation for the phenomenon but for the partitions 
of pith and the hollow space above each mud cocoon. The 
whole arrangement of the nest is so complex that with a 
limited amount of material I am unable to work out a 
final and logical explanation for the entire scheme of 
nidification. For the present the best I can do is to 
