182 Trans. Acad. Sci. of St. Louis 
mortar. Between 11:10 and 2:30, the burrow was dug 
and the chimney built up to a height of % inch; from 
that time until five o’clock, nothing more was done. 
Like A. abrupia, these bees build very definite cups of 
mud within the burrows, in which to oviposit. Fig. 11 
shows a group of such cells—some of them opened to 
show the pupae within, while Fig. 12 shows the pupae , 
in two stages of development. The interior wall of this 
mud cup is varnished with some substance which renders 
it waterproof, a condition we have already described for 
A, abrupta. 
Halictus bee, Halictus (Chloralictus) zephyrus Sm. 
[J. C. Crawford]. 
A small burrow which went down vertically on the 
top of the bank first attracted my attention in 1917. It 
contained a pair of these Halictus bees. One of them, 
probably the male, closed the aperture of the burrow 
with his head, and prevented his consort from entering 
until it suited his whim to admit her. This was the only 
nest of this species found that year, and it now seems 
likely that in taking the pair for identification, I exter- 
minated this species in this locality, for in the two years 
following none appeared. 
The species must have been reinstated, however, be- 
cause in 1920, three burrows were again discovered, and 
in 1921, a dozen nests were there. They dug their bur- 
rows horizontally into the face of the clay bank near the 
base. Below each burrow was a little mound of pulver- 
ized earth. It was at length discovered that several 
adults occupied one gallery, and the nesting cells 
branched off from either side of this gallery (Fig. 13). 
