OCT. 1906. OUR KNOWLEDGE OF THE VISUAL MEMORY OF BEES. 
139 
ing three visits to the nest within 27 minutes. This bee seemed 
to possess a certain knowledge of the locality, since it always 
found the entrance to the nest, hidden among the grass on a hill- 
side, nearly as easily as the owner itself. At that time I was under 
the impression that it was always the same individual returning to 
the nest. 
Last year at the end of September I dug a nest of the same 
species of leaf-cutter bee out of a clay-bank at Milwaukee, and 
after having replaced the earth, and in this way removed all traces 
of the nest, I was surprised to see a parasitic bee, also Coelioxys 
rufit arsis, appear near the former site of the nest, and hunt around 
as eagerly as if it was looking for a nest of its own. This obser- 
vation strengthened me in the belief that parasitic bees, or some of 
them at least, after having come across a suitable nest of a host- 
bee, become acquainted with the locality, and return to the nest 
from time to time. 
In order to settle this question it seemed to me essential to 
follow up the actions of a parasitic bee from the time that it 
made its first acquaintance with a nest of a host-bee. Such an 
opportunity presented itself in the summer of the present year, 
and I offer an account of the observations in detail, as contained 
in my notes. 
August 12, 1906. 
A nest of Golletes eulophi Rob. is situated in a clay-bank in 
Lake Woods (between Milwaukee and Whitensh Bay) , the open- 
ing- to the nest being about 3 dm. below the top of the bank. 
A specimen of a parasitic bee, Argyroselenis minima Rob. comes 
flying- leisurely along the bank, examining every hole or crevice 
on the look-out for a nest of its host-bee. It discovers the nest 
of Golletes, and shows much excitement, crawling over the ground 
with quivering wings, approaching the nest from different sides, 
and looking in, but not entering. It soon takes up a position on 
a small plant about 2 dm. above the nest, and waits patiently 
and motionless until the owner arrives with its load of pollen 
and honey, and disappears in the nest. Thereupon Argyroselenis 
becomes restless, undertakes a general preening of its body, 
the antennae first and again becomes quiet. After the departure 
of the owner, the parasite first goes through the preening process. 
