166 Trans. Acad. Sci. of St. Louis 
from five to seven p. m., 35 adult Xylocopa returned to 
the colony and quietly crept into their burrows! This 
certainly shows how an observation must be made 
from every possible angle before one may dare to be 
satisfied with an answer. Fourteen of these were cap- 
tured and examined; twelve were females and two were 
males. The presence of the males made me wonder 
whether they were the remainder of the first generation, 
or the forerunners of the second. I cannot imagine just 
what was their business abroad which kept them away 
from home all day thus, day after day, at a time when 
they were not gathering provisions of any kind for the 
nest. May it be that they were out seeking food to gorge 
and fatten themselves before beginning the arduous 
tasks of nidification? From this time on the population 
again waned, until by the middle of September they were 
seldom seen. Long after the others had disappeared 
from view, one lone mother was seen going into her 
burrow on October 13. 
Just as the mining bees make way for numerous other 
species by bequeathing to them their old burrows, 8o 
Xylocopa makes it possible for two species of wasps, 
Chlorion (Isodontia) auripes and Monobia quadridens 
to inhabit the locality. For details of the behavior of 
these sub-tenants and for details of parasitism on the 
carpenter-bee, and for the relation of the bee to weather 
conditions, see later pages. 
The mining bee, Anthophora abrupta Say [S. A. 
Rohwer]. 
The most important of the pioneers getting a foothold 
in the clay bank were two species of mining bees, one 
supplementing the other beautifully in the point of time. 
