The Ecology of a Sheltered Clay Bank 223 
more than one generation each year. This made a par- 
ticularly difficult situation for the species of hosts which 
produced but one generation each year. The first adults 
that emerged in the spring, lived and disappeared 
simultaneously with the Anthophora that closed their 
life cycle about the middle of July. The eggs deposited 
by the first lot of adult parasites produced adults later 
in the summer. A careful and frequent examination 
showed that the Chalcids were not in evidence from the 
time of their waning and first disappearance, July 16, 
up until September 3, when they re-appeared after an 
interval of forty-eight days. This second generation 
also comprised an enormous population. Many of these 
were seen also to enter the bee burrows, and some of 
the bee cells dug up later also contained these Chalcids 
in the pupal stage. 
Not all of them succeeded in their parasitic plan of 
existence; some fell prey to other inhabitants early in 
life. On the first day of the appearance of the second 
brood, seven were taken dead from the spiders’ webs 
nearby, and elsewhere in these pages is recorded the 
fact that Vespa germanica was making regular trips, 
carrying them off day after day to her nest. 
On September 6, while the numbers flying about seemed 
just as great, still many were found dead about the bank; 
[ cannot account for this, since this early date seems 
hardly time for a natural death. These may have been 
the dead of the previous generation, or those of the 
Present generation that had perished before emergence, 
Which some industrious Trypoxylon wasps had swept 
out of the old burrows that they were renovating for 
their own use. Mortality was really upon them, how- 
ever, because by September 12 a marked reduction in 
