The Ecology of a Sheltered Clay Bank 165 
about the bees’ tunnels; hence it is probable that this 
parasite was largely responsible for the small number 
of bees, as well as of the mud wasps, Monobia quadri- 
dens, and the grass-carrier wasps, Chlorion (Isodontia) 
auripes, which occupied the old tunnels of the carpenter- 
bees. The details given later under the subject of para- 
sites will show an enormous increase at that time in the 
number of adults of the A. tigrina parasite, 
So the record for the second generation continued dis- 
mal; on August 31, barely two bees were busy, and by 
the middle of September none at all were to be seen. 
During the summer of 1919 no observations could be 
made, so we do not know by what struggles or turns of 
fortune Xylocopa again came into her own, but in the 
following spring, on May 27,* 1920, they were once more 
fairly abundant. Their emergence had probably just 
occurred when I arrived upon the scene, for they were 
not tunneling, neither were they carrying pollen, but 
both sexes were in a gleeful mood of courtship. 
Several days later others were often seen refresh- 
ing themselves on the blackberry blossoms, while sev- 
eral returning females were so heavily laden with green 
pollen that much of it would spill in a delicate shower 
as they tried to gain entrance to the home. During the 
week of June 13 to June 19, eight mothers were at work 
on their nests. Since only these eight remained to work, 
out of the large number in the courtship dance, it leads 
one to suspect that a very large proportion of the latter 
group were males. During the days of June 28th and 
29th, I kept a very careful watch and was startled by the 
revelation which met my eyes; during the two hours 
*In 1922 they were flying about as early as April 7. One newly 
dead bee was taken from a spider’s web. 
