A NOTE ON TRYPARGILUM ARIZONENSE 
IN TRAP NESTS FROM ARIZONA, WITH A 
REVIEW OF PREY PREFERENCES AND 
COCOON STRUCTURE IN THE 
GENUS (HYMENOPTERA, SPHECIDAE)* 
By Robert V/. Matthews and Janice R. Matthews 
Museum of Comparative Zoology 
In early July, 1965, trap nests were placed out in two open areas 
in Tucson, Pima Co., Arizona. At the USDA Experiment Station 
farm, 8 blocks of 6 nests each were situated upon the north- and 
south-facing weathered windowsills of an abandoned storage shed, 
surrounded by low weeds and sheep pasture. About one mile away, 
an equal number of nests were placed at various points upon an 
exposed brick wall along a graveled, sparsely weedy parking lot in a 
residential area. All nests in both areas were placed from 5 to 8 feet 
above the ground. Three bore diameters and lengths were available 
in about equal numbers: inch diameter bores, 77 mm long; 3/16 
inch, 124 mm long; and % inch, no mm long. 
Of 56 completed nests collected by late August, 29 proved to be 
Trypctrgilum arizonense Fox, a species widely distributed in the 
western United States. Nothing has been previously reported on its 
biology except a questionable record (under the name rufozonalis) 
claiming it to be dug from nests in a clay bank in Nebraska (Smith, 
1908). This paper presents information on life history, nest archi- 
tecture and prey preferences of T. arizonense and attempts to relate 
certain data to those recorded for other species of Trypargilum. 
Life History. The egg of Trypargilum arizonense is laid on the 
venter of the abdomen of the last (outermost) spider placed in the 
cell. No information was obtained on developmental stages, but the 
larva has been described by Evans (1957). As is true for most 
other Trypargilum species, the cocoon is dark brown, heavily var- 
nished and brittle, and enclosed in a delicate silken matrix. The 
cocoon shape is, however, quite clearly diagnostic (Fig. 1). At the 
anterior end, as in T. clavatum (see Krombein, 1967), the cocoon 
is truncate and bears a pale collar projecting about 0.5 mm outward; 
however, it differs from clavatum in lacking an anterior nipple. The 
collar has a grainy appearance as though particles from the cell parti- 
tion had been incorporated into it, and the area inside the collar 
appears incompletely varnished or semi-translucent. At the rounded 
* Manuscript received by the editor 6 September 1968. 
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