286 
Psyche 
[September 
Figures 1 and 2. Diagrams of Trypargilum cocoons with the silken 
matrix removed ; both drawn to the same scale. Anterior ends are at the 
right. Fig. 1. T. arizonense. Fig. 2. T. politum, arrows indicate the 
portion encircled by the pebble girdle. 
posterior end, the cocoon bulges very slightly, especially where the 
meconium has been deposited. A series of 1 1 cocoons from ^4 inch 
diameter bores averaged 10.8 mm long (range, 9.5-1 2.0 mm) ; 12 
cocoons from 3/16 inch diameter bores averaged 11.1 mm (range, 
10.0-12.5 mm). No correlations of cocoon length or cell position 
and adult sex were made. Twenty-four females and 16 males were 
reared from the nests. An unidentified chrysidid which escaped from 
one nest was the only parasite found. 
Emergences of adult T. arizonense during August and September 
1965 suggested more than one generation per year; furthermore, 
because trap nests were not placed out until July ? it seems likely that 
the nesting wasps were themselves second-generation individuals. 
Therefore, it seems likely that T. arizonense in Tucson probably 
has at least two, perhaps three or more, generations per year. 
One other species of Trypargilmn , T. t. tridentatum Packard, 
also used the trap nests and may possibly have competed for the 
intermediate (3/16") bores; however, only 3 tridentatum nests 
were obtained, 2 in 3/16" and 1 in a }i" bore. No prey records for 
