io8 
Psyche 
[June 
army barracks. I have also found them building their own cells with- 
in the empty cells of Trypoxylon politum (Say) nests. 
Nest — The nest (fig. i) typically consists of from one to twelve 
small, fragile, mud cells. There is no specific arrangement of the 
cells: they may be constructed side by side, end to end, or in small 
clusters. Since they are often built in small depressions and cracks, 
the size of the particular niche available for nesting often determines 
the number of cells that can be constructed. The cells vary in size 
from 6-IO mm in length and from 4-5 mm in width. 
Nesting behavior — The full length of the daily activity period 
is not known. My observations were carried out from August 7th 
to August 29, primarily in the late afternoon. On two occasions 
I visited the Urbana nesting site at 8 AM, but there was no apparent 
activity on either occasion. On August 7th the last female observed 
was at 5:45 PM, on August 9th at 5:25 PM, and on August 13 
at 5 128 PM. 
Construction of the cell was observed in its entirety only once 
(note 158). On this occasion I arrived at the nest at 3:40 PM and 
found a female in the process of closing the third cell. She was 
bringing in loads of mud in her mandibles and then, using only her 
mandibles for manipulating it, was applying it to the cell. It soon 
became apparent that more than a closure was involved. She was 
beginning a new cell directly on the end of the old one. It was thus 
impossible to be certain exactly how many trips were required to 
construct the new one. From the time that I arrived, however, until 
the new cell was completed, 19 trips were made for mud. The female 
of nest 158 spent 75-330 sec away from the cell (meanztstd. error = 
1 47.7 ±22.4, N = 15 observations), and 15-390 sec at the cell 
(meandbstd. error — 136.2=^23.0, N = 16 observations). 
P. koreense provisions her cells with small spiders, a feature which 
is apparently characteristic of the genus. Two cells (notes 136 and 
158) were observed during the process of provisioning. Although it 
is difficult to be certain, without photographic evidence, I am con- 
vinced that when approaching a cell, the female carries the spider, 
which she has stung and paralyzed, solely by her mandibles. She 
approaches quickly and hovers momentarily about a foot in front 
of her cell before landing near the entrance. She then immediately 
walks to the cell carrying the spider in her mandibles, enters head 
Explanation of Plate 5 
Fig. 1. — Cluster of five cells of Pison koreense. Fig. 2. — Single cell. 
Fig. 3. — Cocoon. Fig. 4 — Egg of P. koreense on prey. 
