The Ecology of a Sheltered Clay Bank 231 
become so specialized as to require a specific host, for 
we have often seen it behave so with other wasps else- 
- where, 
Argyromoeba anale Say. One specimen of this para- 
sitic fly was on the bank September 7, 1917. 
Argyromoeba oedipus Fab. [F. Knab]. Six specimens 
of this parasite were seen about the clay bank on July 
31, one of which actually entered a burrow of the white- 
banded bee, Entechnia taurea. 
Argyromocba fur O. S. [F. Knab]. One was at rest 
on the clay bank on September 3, 1917. In 1918, this 
species, along with all the other life in the unit, appeared 
about a month earlier, or on May 28. (The 1918 material 
was identified by C. T. Greene.) 
Argyromoeba tigrina De G. [F. Knab]. This para- 
Sitic fly (Fig. 18) first appeared on August 8, 1917. At 
first there were only three individuals; two days later 
they were present in very great numbers. They frisked 
and flitted about in the sunlight, stopping to rest for 
long periods on the wooden part of the porch and in the 
direct sunlight. When at rest thus they could easily be 
Picked up with the fingers. The peculiar life history of 
this fly enables us to know absolutely that they had not 
flown to the bank from afar, but had actually emerged 
on the scene. The tell-tale evidence is this: in trans- 
forming to adulthood, this species leaves the home of 
its host while it is still in the pupal stage and, upon 
gaining its freedom transforms into the adult and 
leaves the old shedding-skin (Fig. 19) on the surface 
near the point where it emerged. In many places on 
the face of the clay bank, and at its base, up among the 
Wooden partitions very near to the tunnels of the car- 
Penter-bees, Monobia wasps or grass-carrier wasps, and 
