1968] 
Matthews and Matthews — Trypargilum 
287 
tridentatum were obtained in our study, but Krombein (1967) gives 
extensive documentation of prey and nest architecture for this species 
from four localities in Arizona. Two of our tridentatum nests were 
parasitized by unidentified chrysidid wasps. 
Nest Architecture. Table 1 summarizes various features of the 
nest architecture for the 29 completed nests obtained. As is the case 
for most twig nesting wasps and bees, a typical nest consists of a 
linear series of provisioned cells separated by partitions, an empty 
vestibular cell, and an outer plug. The partitions and plug were of 
mud ; partitions were uniformly about 1 mm thick, but the nest 
plug was of variable depth (see Table 1) and usually not quite 
flush with the nest entrance. Nearly all nests were begun with a 
scant mud spot at the bottom of the bore; 4 nests also had an empty 
space preceding the first provisioned cell. No intercalary cells were 
found. 
Length of the provisioned cells was quite variable, probably at least 
in part due to differences in size and packing of prey. The last pro- 
visioned cell, in particular, was commonly much longer than the 
others; omitting this cell leads to an “amended” cell length (Table 1) 
which is less variable and smaller^ a more accurate indication of the 
usual cell size. 
Table 1. Comparison of Trypargilum arizonense nest archi- 
tecture in two bore sizes, Tucson, Arizona, July-August 1965. 
Measurements are averages in millimeters; ranges are given in 
parentheses. 
no. of completed nests 
no. of completed cells 
nest plug thickness 
nest plug recession 
vestibular cell length 
provisioned cells per nest 
provisioned cell length 
“amended” cell length 
J4" bore, 
77 mm long 
19 
5i 
2.9 (1-5) 
1.3 (0-4) 
25-3 (u-55) 
2.7 (i- 4) 
15.9 (10-52) 
13. 1 (10-19) 
3/16" bore, 
124 mm long 
10 
34 
2.6 (1-4) 
1.0 (0-3) 
32-5 (13-50) 
3-4 (2-5) 
22.2 (13-57) 
18.4 (13-25) 
Prey. Table 2 lists the spiders taken as prey by T. arizonense ; 
interestingly, a majority (70%) were immature. There were 8 to 
19 spiders per cell (mean 11.8) in 16 fully provisioned cells; differ- 
ences in spider size probably account for most of this variation, and 
