The Ecology of a Sheltered Clay Bank 193 
inhabitants themselves or occasional visitors to the set- 
tlement. That this was a favorable place for them to 
flourish and multiply was evidenced by the fact that in 
1917, 20 pits were counted at the foot of the bank; in 
1918, 150 were there, but most of these were gathered 
to send to a friend for study. Hence in the following 
years they appeared again in about the same numbers 
as in 1917, at the base and also on top of the bank. Of 
course we should bear in mind that the ant-lions, by 
virtue of their peculiar mode of development, are well 
prepared to survive and flourish, so that, like the poor, 
we shall have them always with us. They neither perish 
nor migrate if food becomes scarce for a time, but they 
simply lie dormant, and put off growing and transform- 
ing for a year or so until food again becomes plentiful. 
Thus, an examination on October 13 revealed many 
ant-lions in all stages of development; some were re- 
constructing their pits in my presence, others were 
larvae in all sizes from small to large, with pits in pro- 
Portionately varying sizes. Precisely these conditions 
were found at all other seasons, from the opening of 
spring to the close of autumn. This shows that they 
have no set time of the year for their metamorphosis, 
but change whenever they have reached a certain stage, 
regardless of the time of the year. Some that were 
brought into the house and fed abundantly on flies 
8rew rapidly, pupated in a few days and emerged as 
adults from three to four weeks later. 
One must not forget to consider the life habits in rela- 
tion to the environment, when contrasting the develop- 
ment of the ant-lions with that of the bees. The larvae 
of the bees are supplied with sufficient food to carry them 
through their development without their exertion, while 
