The Ecology of a Sheltered Clay Bank 199 
for their prey. These details of the life history will be 
presented in a later publication. 
Trypoxylon albopilosum Fox [S. A. Rohwer]. 
This wasp, with habits similar to those of T. clavatum, 
likewise oceupied the old burrows of the mining bees. 
It was first observed on June 28, 1917, when several 
mothers were at work. They always appeared only in 
such small numbers, however, that I could not accurately 
define any seasons or generations for them, only that 
they were to be seen occasionally until early Septem- 
ber. Since I opened part of the nests to study the con- 
tents, it was only natural that their population dwindled 
away, until in 1920 one lone survivor was observed, The 
relation of this species to their neighbors was the same 
as that of T. clavatum. 
The Monobia mud-wasp, Monobia quadridens. Lin- 
naeus. 
This wasp, commonly called the carpenter mud-wasp, 
but, according to our account in ‘‘Wasp Studies Afield”’ 
not a carpenter at all, can be regarded as only a sec- 
ondary inhabitant of the clay bank, since it made no 
nest of its own, but occupied that of the carpenter-bee, 
Xylocopa virginica. These wasps were seen each year 
bringing in mud for partitions and caterpillars for food 
for their young. On one occasion, as previously re- 
corded, one Monobia mother actually utilized the tunnel 
ofa mining-bee, carrying in caterpillars and sealing up 
the opening with mud. 
This wasp appeared from year to year in very limited 
numbers, not more than 6 or 8 being present at work at 
