The Ecology of a Sheltered Clay Bank 241 
emerging later, conformed nicely to the precedent set 
by the spring Hymenoptera in the year 1918, when the 
meteorological conditions were very different from 1917. 
This bee population emerged in 1917 on July 16 and in 
1918 with a more favorable temperature 18 days earlier 
on June 28. In this species I found, in so far as the 
records were kept, that they responded, by emerging 
from the pupal condition, to a temperature of 77°. Using 
the same weather records as a basis, we find that for the 
fifteen days preceding their emergence on July 16, 1917, 
we had an average mean temperature of 77 2/15°. In 
1918, their appearance was earlier, June 28, and the 
average mean temperature for the period of fifteen days 
preceding this was 77 2/3° F. 
Thus, we can see in the emergence of this hymenop- 
terous population a very definite response to tempera- 
ture, and not an emergence correlated with the length of 
time the organisms had spent in the ground as larvae or 
pupae. This is quite reasonable, as is already known, 
the time spent in the various stages is lengthened by 
cold, and the development is accelerated by warmth. 
‘All this seems, in so far as these Hymenoptera are con- 
cerned, not to apply merely to a single species, but to 
indicate a law influencing all life under these conditions. 
(b) Relation of population to light and sunshine. 
The Hymenoptera are generally regarded as lovers of 
the light and sunshine, and especially is this true of 
the flower-frequenting bees and wasps; they are gen- 
erally to be seen foraging among the blossoms, and then 
indeed may we call them children of the sun. Here we 
are interested in the three phases: (a) the relation of 
the position of the nests to the sunlight, (b) the rela- 
