Field Studies of the Non-Social Wasps 391 
smaller individuals. There was an open gallery of 34 
inch at the top, which could have been used to afford 
more space to the inmates below if desired, or to make 
two additional cells if the mother had been so inclined. 
We shall not reproach her for omitting the additional 
cells, since she may have fallen victim to tragedy. But 
who are we that we should accuse her of lack of wisdom 
in crowding the other cells; she may have known her 
business better than we know. Fabre tells us about 
another creature that knows the sex of each egg, and 
builds a small chamber or a large one for it, according 
to whether it be male or female, and also supplies food 
accordingly. But on the whole, this nest was more 
carelessly constructed than the others; there was much 
rough pith remaining on the walls, with some mud 
and bits of old cocoons of other species still adhering; 
all this could have been scraped off, as in the other nests, 
and put into good roofs. Then these partitions, unlike 
the others, were very thin and frail, composed for the 
most part of mud. From examining this specimen, I 
conclude that the composition of the unknown substance 
in the partitions in some other nests in this species is the 
scrapings of the wall pith combined with the adhering 
bits of rubbish, cocoons and mud. Another noticable 
feature was that in this case we did not find the double 
partition walls, but instead the thin, frail, single ones, 
despite the fact that abundant material was at hand for 
the work right within the tunnel. 
When we compare this slovenly specimen with the fine 
work of other members of this group, we see clearly that 
variation in behavior exists, and is due probably to in- 
dividual temperament or experience. We note also the 
fact that some get away from the strict rule of always 
getting mud for partitions, but have ‘‘learned’’ that in 
